Added a test block for a dynamic dropdown.

tests/blocks/test_blocks.js

@@ -19,6 +19,8 @@
  */
 'use strict';
 
+goog.provide('Blockly.TestBlocks');
+
 Blockly.defineBlocksWithJsonArray([  // BEGIN JSON EXTRACT
   {
     "type": "empty_block",
@@ -571,3 +573,61 @@ Blockly.Blocks['empty_block_with_mutator'] = {
     this.setMutator(new Blockly.Mutator(['math_number']));
   }
 };
+
+Blockly.Blocks['test_dropdown_dynamic'] = {
+  init: function() {
+    var dropdown = new Blockly.FieldDropdown(this.dynamicOptions);
+    this.appendDummyInput()
+      .appendField('dynamic')
+      .appendField(dropdown, 'OPTIONS');
+  },
+
+  dynamicOptions: function() {
+    if (!Blockly.TestBlocks.dynamicDropdownOptions_.length) {
+      return [['', 'OPTION0']];
+    }
+    return Blockly.TestBlocks.dynamicDropdownOptions_;
+  }
+};
+
+/**
+ * An array of options for the dynamic dropdown.
+ * @type {!Array<!Array>}
+ * @package
+ */
+Blockly.TestBlocks.dynamicDropdownOptions_ = [];
+
+/**
+ * Handles "add option" button in the field test category. This will prompt
+ * the user for an option to add.
+ * @package
+ */
+Blockly.TestBlocks.addDynamicDropdownOption_ = function() {
+  Blockly.prompt('Add an option?', '', function(text) {
+    if (text) {
+      // Do not remove this log! Helps you know if it was added correctly.
+      console.log('Adding option: ' + text);
+      Blockly.TestBlocks.dynamicDropdownOptions_.push([text,
+        'OPTION' + Blockly.TestBlocks.dynamicDropdownOptions_.length]);
+    }
+  })
+};
+
+/**
+ * Handles "remove option" button in the field test category. This will prompt
+ * the user for an option to remove.
+ * @package
+ */
+Blockly.TestBlocks.removeDynamicDropdownOption_ = function() {
+  Blockly.prompt('Remove an option?', '', function(text) {
+    for (var i = 0, option;
+         option = Blockly.TestBlocks.dynamicDropdownOptions_[i];
+         i++) {
+      if (option[0] == text) {
+        // Do not remove this log! Helps you know if it was removed correctly.
+        console.log('Removing option: ' + text);
+        Blockly.TestBlocks.dynamicDropdownOptions_.splice(i, 1);
+      }
+    }
+  })
+};

tests/playground.html

@@ -122,6 +122,7 @@ function start() {
             scaleSpeed: 1.1
           }
       });
+  addToolboxButtonCallbacks();
   // Restore previously displayed text.
   if (sessionStorage) {
     var text = sessionStorage.getItem('textarea');
@@ -138,6 +139,13 @@ function start() {
   taChange();
 }
 
+function addToolboxButtonCallbacks() {
+  workspace.registerButtonCallback(
+      'addDynamicOption', Blockly.TestBlocks.addDynamicDropdownOption_);
+  workspace.registerButtonCallback(
+      'removeDynamicOption', Blockly.TestBlocks.removeDynamicDropdownOption_);
+}
+
 function changeTheme() {
   var theme = document.getElementById('themeChanger');
   if (theme.value === "modern") {
@@ -1182,6 +1190,9 @@ h1 {
       <block type="example_dropdown_long"></block>
       <block type="example_dropdown_images"></block>
       <block type="example_dropdown_images_and_text"></block>
+      <button text="add option" callbackKey="addDynamicOption"></button>
+      <button text="remove option" callbackKey="removeDynamicOption"></button>
+      <block type="test_dropdown_dynamic"></block>
       <label text="Others"></label>
       <block type="example_angle"></block>
       <block type="example_date"></block>