Fix bug #904 by explicitly grabbing focus on the workspace svg element. (#964)

core/workspace_svg.js

@@ -1358,6 +1358,10 @@ Blockly.WorkspaceSvg.prototype.markFocused = function() {
     this.options.parentWorkspace.markFocused();
   } else {
     Blockly.mainWorkspace = this;
+    // We call e.preventDefault in many event handlers which means we
+    // need to explicitly grab focus (e.g from a textarea) because
+    // the browser will not do it for us.
+    this.getParentSvg().focus();
   }
 };