Merge remote-tracking branch 'Google/master' into google-master-april-1

# Conflicts:
#	blockly_compressed_horizontal.js
#	blockly_uncompressed_vertical.js
#	blocks_compressed.js
#	core/block.js
#	core/block_svg.js
#	core/blockly.js
#	core/connection.js
#	core/field_textinput.js
#	core/workspace_svg.js
#	generators/lua/lists.js
#	generators/lua/text.js
#	msg/js/he.js
#	msg/js/id.js
#	msg/js/sr.js
#	msg/js/zh-hant.js
#	msg/json/en.json

core/workspace.js

@@ -153,9 +153,16 @@ Blockly.Workspace.prototype.getAllBlocks = function() {
  * Dispose of all blocks in workspace.
  */
 Blockly.Workspace.prototype.clear = function() {
+  var existingGroup = Blockly.Events.getGroup();
+  if (!existingGroup) {
+    Blockly.Events.setGroup(true);
+  }
   while (this.topBlocks_.length) {
     this.topBlocks_[0].dispose();
   }
+  if (!existingGroup) {
+    Blockly.Events.setGroup(false);
+  }
 };
 
 /**
@@ -232,12 +239,21 @@ Blockly.Workspace.prototype.undo = function(redo) {
   events = Blockly.Events.filter(events, redo);
   Blockly.Events.recordUndo = false;
   for (var i = 0, event; event = events[i]; i++) {
-    console.log(event);
     event.run(redo);
   }
   Blockly.Events.recordUndo = true;
 };
 
+/**
+ * Clear the undo/redo stacks.
+ */
+Blockly.Workspace.prototype.clearUndo = function() {
+  this.undoStack_.length = 0;
+  this.redoStack_.length = 0;
+  // Stop any events already in the firing queue from being undoable.
+  Blockly.Events.clearPendingUndo();
+};
+
 /**
  * When something in this workspace changes, call a function.
  * @param {!Function} func Function to call.
@@ -328,6 +344,8 @@ Blockly.Workspace.getById = function(id) {
 
 // Export symbols that would otherwise be renamed by Closure compiler.
 Blockly.Workspace.prototype['clear'] = Blockly.Workspace.prototype.clear;
+Blockly.Workspace.prototype['clearUndo'] =
+    Blockly.Workspace.prototype.clearUndo;
 Blockly.Workspace.prototype['addChangeListener'] =
     Blockly.Workspace.prototype.addChangeListener;
 Blockly.Workspace.prototype['removeChangeListener'] =