diff --git a/tests/drag_tests.html b/tests/drag_tests.html
new file mode 100644
index 000000000..06acef0f5
--- /dev/null
+++ b/tests/drag_tests.html
@@ -0,0 +1,606 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>Blockly Playground</title>
+<script src="../blockly_uncompressed.js"></script>
+<script src="../msg/messages.js"></script>
+<script src="../blocks/logic.js"></script>
+<script src="../blocks/loops.js"></script>
+<script src="../blocks/math.js"></script>
+<script src="../blocks/text.js"></script>
+<script src="../blocks/lists.js"></script>
+<script src="../blocks/colour.js"></script>
+<script src="../blocks/variables.js"></script>
+<script src="../blocks/procedures.js"></script>
+<script>
+'use strict';
+// Depending on the URL argument, render as LTR or RTL.
+var rtl = (document.location.search == '?rtl');
+var workspace = null;
+var fakeDragQueue = [];
+
+
+function start() {
+  var toolbox = document.getElementById('toolbox');
+  workspace = Blockly.inject('blocklyDiv',
+          {comments: true,
+           disable: true,
+           collapse: true,
+           grid:
+             {spacing: 25,
+              length: 3,
+              colour: '#ccc',
+              snap: true},
+           maxBlocks: Infinity,
+           media: '../media/',
+           readOnly: false,
+           rtl: rtl,
+           scrollbars: true,
+           toolbox: toolbox,
+           zoom:
+             {controls: true,
+              wheel: true,
+              startScale: 1.0,
+              maxScale: 4,
+              minScale: .25,
+              scaleSpeed: 1.1}
+          });
+  // Restore previously displayed text.
+  if (sessionStorage) {
+    var text = sessionStorage.getItem('textarea');
+    if (text) {
+      document.getElementById('importExport').value = text;
+    }
+    // Restore event logging state.
+    var state = sessionStorage.getItem('logEvents');
+    logEvents(Boolean(Number(state)));
+  } else {
+    // MSIE 11 does not support sessionStorage on file:// URLs.
+    logEvents(false);
+  }
+  taChange();
+
+  window.setTimeout(function() {
+    airstrike(100);
+    fakeManyDrags();
+  }, 1000);
+}
+
+function toXml() {
+  var output = document.getElementById('importExport');
+  var xml = Blockly.Xml.workspaceToDom(workspace);
+  output.value = Blockly.Xml.domToPrettyText(xml);
+  output.focus();
+  output.select();
+  taChange();
+}
+
+function fromXml() {
+  var input = document.getElementById('importExport');
+  var xml = Blockly.Xml.textToDom(input.value);
+  Blockly.Xml.domToWorkspace(xml, workspace);
+  taChange();
+}
+
+// Disable the "Import from XML" button if the XML is invalid.
+// Preserve text between page reloads.
+function taChange() {
+  var textarea = document.getElementById('importExport');
+  if (sessionStorage) {
+    sessionStorage.setItem('textarea', textarea.value);
+  }
+  var valid = true;
+  try {
+    Blockly.Xml.textToDom(textarea.value);
+  } catch (e) {
+    valid = false;
+  }
+  document.getElementById('import').disabled = !valid;
+}
+
+function logEvents(state) {
+  var checkbox = document.getElementById('logCheck');
+  checkbox.checked = state;
+  if (sessionStorage) {
+    sessionStorage.setItem('logEvents', Number(state));
+  }
+  if (state) {
+    workspace.addChangeListener(logger);
+  } else {
+    workspace.removeChangeListener(logger);
+  }
+}
+
+function logger(e) {
+  console.log(e);
+}
+
+function airstrike(n) {
+  var prototypes = [];
+  var toolbox = document.getElementById('toolbox');
+  var blocks = toolbox.getElementsByTagName('block');
+  for (var i = 0, block; block = blocks[i]; i++) {
+    prototypes.push(block.getAttribute('type'));
+  }
+  for (var i = 0; i < n; i++) {
+    var prototype = prototypes[Math.floor(Math.random() * prototypes.length)];
+    var block = workspace.newBlock(prototype);
+    block.initSvg();
+    block.getSvgRoot().setAttribute('transform', 'translate(' +
+        Math.round(Math.random() * 450 + 40) + ', ' +
+        Math.round(Math.random() * 600 + 40) + ')');
+    block.render();
+  }
+}
+
+function fakeDrag(id, dx, dy, opt_workspace) {
+  var ws = opt_workspace ? opt_workspace : Blockly.getMainWorkspace();
+  var blockToDrag = ws.getBlockById(id);
+
+  if (!blockToDrag) {
+    return;
+  }
+  var blockTop = blockToDrag.svgGroup_.getBoundingClientRect().top;
+  var blockLeft = blockToDrag.svgGroup_.getBoundingClientRect().left;
+
+  // Click somewhere on the block.
+  var mouseDownEvent = new MouseEvent('mousedown',
+      {clientX: blockLeft + 5, clientY: blockTop + 5});
+  blockToDrag.onMouseDown_(mouseDownEvent);
+
+  // Throw in a move for good measure.
+  window.setTimeout(
+    function() {
+      var mouseMoveEvent = new MouseEvent('mousemove',
+          {clientX: blockLeft + dx,
+          clientY: blockTop + dy});
+      blockToDrag.onMouseMove_(mouseMoveEvent);
+
+      // Drop at dx, dy.
+      window.setTimeout(
+        function() {
+          var mouseUpEvent = new MouseEvent('mouseup',
+              {clientX: blockLeft + dx,
+              clientY: blockTop + dy});
+          blockToDrag.onMouseUp_(mouseUpEvent);
+
+          window.setTimeout(fakeDragWrapper(), 100);
+        }, 30);
+    }, 30);
+};
+
+function fakeDragWrapper() {
+  var dragInfo = fakeDragQueue.pop();
+  if (dragInfo) {
+    fakeDrag(dragInfo.id, dragInfo.dx, dragInfo.dy, dragInfo.workspace);
+  }
+}
+
+function fakeManyDrags() {
+  console.log('fake many drags');
+  var ws = Blockly.getMainWorkspace();
+  var blockList = ws.getAllBlocks();
+  for (var i = 0; i < 2 * blockList.length; i++) {
+    fakeDragQueue.push(
+      {
+        id: blockList[Math.round(Math.random() * (blockList.length - 1))].id,
+        // Move some blocks up and to the left, but mostly down and to the right.
+        dx: Math.round((Math.random() - 0.25) * 200),
+        dy: Math.round((Math.random() - 0.25)* 200),
+        workspace: ws
+      });
+  }
+  fakeDragWrapper();
+};
+
+function spaghetti(n) {
+  var xml = spaghettiXml;
+  for(var i = 0; i < n; i++) {
+    xml = xml.replace(/(<(statement|next)( name="DO0")?>)<\//g,
+        '$1' + spaghettiXml + '</');
+  }
+  xml = '<xml xmlns="http://www.w3.org/1999/xhtml">' + xml + '</xml>';
+  var dom = Blockly.Xml.textToDom(xml);
+  console.time('Spaghetti domToWorkspace');
+  Blockly.Xml.domToWorkspace(dom, workspace);
+  console.timeEnd('Spaghetti domToWorkspace');
+}
+var spaghettiXml = [
+  '  <block type="controls_if">',
+  '    <value name="IF0">',
+  '      <block type="logic_compare">',
+  '        <field name="OP">EQ</field>',
+  '        <value name="A">',
+  '          <block type="math_arithmetic">',
+  '            <field name="OP">MULTIPLY</field>',
+  '            <value name="A">',
+  '              <block type="math_number">',
+  '                <field name="NUM">6</field>',
+  '              </block>',
+  '            </value>',
+  '            <value name="B">',
+  '              <block type="math_number">',
+  '                <field name="NUM">7</field>',
+  '              </block>',
+  '            </value>',
+  '          </block>',
+  '        </value>',
+  '        <value name="B">',
+  '          <block type="math_number">',
+  '            <field name="NUM">42</field>',
+  '          </block>',
+  '        </value>',
+  '      </block>',
+  '    </value>',
+  '    <statement name="DO0"></statement>',
+  '    <next></next>',
+  '  </block>'].join('\n');
+
+</script>
+
+<style>
+html, body {
+  height: 100%;
+}
+body {
+  background-color: #fff;
+  font-family: sans-serif;
+  overflow: hidden;
+}
+h1 {
+  font-weight: normal;
+  font-size: 140%;
+}
+#blocklyDiv {
+  float: right;
+  height: 95%;
+  width: 70%;
+}
+#importExport {
+  font-family: monospace;
+}
+</style>
+</head>
+<body onload="start()">
+
+  <div id="blocklyDiv"></div>
+
+  <xml id="toolbox" style="display: none">
+    <category name="Logic" colour="210">
+      <block type="controls_if"></block>
+      <block type="logic_compare"></block>
+      <block type="logic_operation"></block>
+      <block type="logic_negate"></block>
+      <block type="logic_boolean"></block>
+      <block type="logic_null" disabled="true"></block>
+      <block type="logic_ternary"></block>
+    </category>
+    <category name="Loops" colour="120">
+      <block type="controls_repeat_ext">
+        <value name="TIMES">
+          <shadow type="math_number">
+            <field name="NUM">10</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="controls_repeat" disabled="true"></block>
+      <block type="controls_whileUntil"></block>
+      <block type="controls_for">
+        <value name="FROM">
+          <shadow type="math_number">
+            <field name="NUM">1</field>
+          </shadow>
+        </value>
+        <value name="TO">
+          <shadow type="math_number">
+            <field name="NUM">10</field>
+          </shadow>
+        </value>
+        <value name="BY">
+          <shadow type="math_number">
+            <field name="NUM">1</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="controls_forEach"></block>
+      <block type="controls_flow_statements"></block>
+    </category>
+    <category name="Math" colour="230">
+      <block type="math_number" gap="32"></block>
+      <block type="math_arithmetic">
+        <value name="A">
+          <shadow type="math_number">
+            <field name="NUM">1</field>
+          </shadow>
+        </value>
+        <value name="B">
+          <shadow type="math_number">
+            <field name="NUM">1</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_single">
+        <value name="NUM">
+          <shadow type="math_number">
+            <field name="NUM">9</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_trig">
+        <value name="NUM">
+          <shadow type="math_number">
+            <field name="NUM">45</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_constant"></block>
+      <block type="math_number_property">
+        <value name="NUMBER_TO_CHECK">
+          <shadow type="math_number">
+            <field name="NUM">0</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_change">
+        <value name="DELTA">
+          <shadow type="math_number">
+            <field name="NUM">1</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_round">
+        <value name="NUM">
+          <shadow type="math_number">
+            <field name="NUM">3.1</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_on_list"></block>
+      <block type="math_modulo">
+        <value name="DIVIDEND">
+          <shadow type="math_number">
+            <field name="NUM">64</field>
+          </shadow>
+        </value>
+        <value name="DIVISOR">
+          <shadow type="math_number">
+            <field name="NUM">10</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_constrain">
+        <value name="VALUE">
+          <shadow type="math_number">
+            <field name="NUM">50</field>
+          </shadow>
+        </value>
+        <value name="LOW">
+          <shadow type="math_number">
+            <field name="NUM">1</field>
+          </shadow>
+        </value>
+        <value name="HIGH">
+          <shadow type="math_number">
+            <field name="NUM">100</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_random_int">
+        <value name="FROM">
+          <shadow type="math_number">
+            <field name="NUM">1</field>
+          </shadow>
+        </value>
+        <value name="TO">
+          <shadow type="math_number">
+            <field name="NUM">100</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="math_random_float"></block>
+    </category>
+    <category name="Text" colour="160">
+      <block type="text"></block>
+      <block type="text_join"></block>
+      <block type="text_append">
+        <value name="TEXT">
+          <shadow type="text"></shadow>
+        </value>
+      </block>
+      <block type="text_length">
+        <value name="VALUE">
+          <shadow type="text">
+            <field name="TEXT">abc</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="text_isEmpty">
+        <value name="VALUE">
+          <shadow type="text">
+            <field name="TEXT"></field>
+          </shadow>
+        </value>
+      </block>
+      <block type="text_indexOf">
+        <value name="VALUE">
+          <block type="variables_get">
+            <field name="VAR">text</field>
+          </block>
+        </value>
+        <value name="FIND">
+          <shadow type="text">
+            <field name="TEXT">abc</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="text_charAt">
+        <value name="VALUE">
+          <block type="variables_get">
+            <field name="VAR">text</field>
+          </block>
+        </value>
+      </block>
+      <block type="text_getSubstring">
+        <value name="STRING">
+          <block type="variables_get">
+            <field name="VAR">text</field>
+          </block>
+        </value>
+      </block>
+      <block type="text_changeCase">
+        <value name="TEXT">
+          <shadow type="text">
+            <field name="TEXT">abc</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="text_trim">
+        <value name="TEXT">
+          <shadow type="text">
+            <field name="TEXT">abc</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="text_print">
+        <value name="TEXT">
+          <shadow type="text">
+            <field name="TEXT">abc</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="text_prompt_ext">
+        <value name="TEXT">
+          <shadow type="text">
+            <field name="TEXT">abc</field>
+          </shadow>
+        </value>
+      </block>
+    </category>
+    <category name="Lists" colour="260">
+      <block type="lists_create_with">
+        <mutation items="0"></mutation>
+      </block>
+      <block type="lists_create_with"></block>
+      <block type="lists_repeat">
+        <value name="NUM">
+          <shadow type="math_number">
+            <field name="NUM">5</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="lists_length"></block>
+      <block type="lists_isEmpty"></block>
+      <block type="lists_indexOf">
+        <value name="VALUE">
+          <block type="variables_get">
+            <field name="VAR">list</field>
+          </block>
+        </value>
+      </block>
+      <block type="lists_getIndex">
+        <value name="VALUE">
+          <block type="variables_get">
+            <field name="VAR">list</field>
+          </block>
+        </value>
+      </block>
+      <block type="lists_setIndex">
+        <value name="LIST">
+          <block type="variables_get">
+            <field name="VAR">list</field>
+          </block>
+        </value>
+      </block>
+      <block type="lists_getSublist">
+        <value name="LIST">
+          <block type="variables_get">
+            <field name="VAR">list</field>
+          </block>
+        </value>
+      </block>
+      <block type="lists_split">
+        <value name="DELIM">
+          <shadow type="text">
+            <field name="TEXT">,</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="lists_sort"></block>
+    </category>
+    <category name="Colour" colour="20">
+      <block type="colour_picker"></block>
+      <block type="colour_random"></block>
+      <block type="colour_rgb">
+        <value name="RED">
+          <shadow type="math_number">
+            <field name="NUM">100</field>
+          </shadow>
+        </value>
+        <value name="GREEN">
+          <shadow type="math_number">
+            <field name="NUM">50</field>
+          </shadow>
+        </value>
+        <value name="BLUE">
+          <shadow type="math_number">
+            <field name="NUM">0</field>
+          </shadow>
+        </value>
+      </block>
+      <block type="colour_blend">
+        <value name="COLOUR1">
+          <shadow type="colour_picker">
+            <field name="COLOUR">#ff0000</field>
+          </shadow>
+        </value>
+        <value name="COLOUR2">
+          <shadow type="colour_picker">
+            <field name="COLOUR">#3333ff</field>
+          </shadow>
+        </value>
+        <value name="RATIO">
+          <shadow type="math_number">
+            <field name="NUM">0.5</field>
+          </shadow>
+        </value>
+      </block>
+    </category>
+    <sep></sep>
+    <category name="Variables" colour="330" custom="VARIABLE"></category>
+    <category name="Functions" colour="290" custom="PROCEDURE"></category>
+  </xml>
+
+  <h1>Blockly Playground</h1>
+
+  <p><a href="javascript:void(workspace.setVisible(true))">Show</a>
+   - <a href="javascript:void(workspace.setVisible(false))">Hide</a></p>
+
+  <script>
+    if (rtl) {
+      document.write('[ &larr; RTL. Switch to <A HREF="?ltr">LTR</A>. ]');
+    } else {
+      document.write('[ &rarr; LTR. Switch to <A HREF="?rtl">RTL</A>. ]');
+    }
+  </script>
+
+  <p>
+    <input type="button" value="Export to XML" onclick="toXml()">
+    &nbsp;
+    <input type="button" value="Import from XML" onclick="fromXml()" id="import">
+    <textarea id="importExport" style="width: 26%; height: 12em"
+      onchange="taChange();" onkeyup="taChange()"></textarea>
+  </p>
+
+  <p>
+    Stress test: &nbsp;
+    <input type="button" value="Airstrike!" onclick="airstrike(100)">
+    <input type="button" value="Spaghetti!" onclick="spaghetti(8)">
+  </p>
+  <p>
+    Log events: &nbsp;
+    <input type="checkbox" onclick="logEvents(this.checked)" id="logCheck">
+  </p>
+
+</body>
+</html>
