diff --git a/core/block.js b/core/block.js
index 0b0226035..082ca4296 100644
--- a/core/block.js
+++ b/core/block.js
@@ -290,6 +290,19 @@ const Block = function(workspace, prototypeName, opt_id) {
   /** @type {?boolean} */
   this.rendered = null;
 
+  /**
+   * String for block help, or function that returns a URL. Null for no help.
+   * @type {string|Function}
+   */
+  this.helpUrl = null;
+
+  /**
+   * A bound callback function to use when the parent workspace changes.
+   * @type {?function(Abstract)}
+   * @private
+   */
+  this.onchangeWrapper_ = null;
+
   /**
    * A count of statement inputs on the block.
    * @type {number}
diff --git a/core/block_svg.js b/core/block_svg.js
index 54dbdbefd..5fd46d8a7 100644
--- a/core/block_svg.js
+++ b/core/block_svg.js
@@ -209,6 +209,12 @@ const BlockSvg = function(workspace, prototypeName, opt_id) {
    */
   this.renderIsInProgress_ = false;
 
+  /**
+   * Whether mousedown events have been bound yet.
+   * @type {boolean}
+   * @private
+   */
+  this.eventsInit_ = false;
 
   /** @type {!WorkspaceSvg} */
   this.workspace = workspace;
diff --git a/core/comment.js b/core/comment.js
index 8dc56bdb8..30f9aac36 100644
--- a/core/comment.js
+++ b/core/comment.js
@@ -98,6 +98,28 @@ const Comment = function(block) {
    */
   this.onInputWrapper_ = null;
 
+  /**
+   * The SVG element that contains the text edit area, or null if not created.
+   * @type {?SVGForeignObjectElement}
+   * @private
+   */
+  this.foreignObject_ = null;
+
+  /**
+   * The editable text area, or null if not created.
+   * @type {?Element}
+   * @private
+   */
+  this.textarea_ = null;
+
+  /**
+   * The top-level node of the comment text, or null if not created.
+   * @type {?SVGTextElement}
+   * @private
+   */
+  this.paragraphElement_ = null;
+
+
   this.createIcon();
 };
 object.inherits(Comment, Icon);
diff --git a/core/icon.js b/core/icon.js
index aa7195749..3f81e9795 100644
--- a/core/icon.js
+++ b/core/icon.js
@@ -47,33 +47,34 @@ const Icon = function(block) {
    * @type {?SVGGElement}
    */
   this.iconGroup_ = null;
+
+  /**
+   * Whether this icon gets hidden when the block is collapsed.
+   * @type {boolean}
+   */
+  this.collapseHidden = true;
+
+  /**
+   * Height and width of icons.
+   * @const
+   */
+  this.SIZE = 17;
+
+  /**
+   * Bubble UI (if visible).
+   * @type {?Bubble}
+   * @protected
+   */
+  this.bubble_ = null;
+
+  /**
+   * Absolute coordinate of icon's center.
+   * @type {?Coordinate}
+   * @protected
+   */
+  this.iconXY_ = null;
 };
 
-/**
- * Does this icon get hidden when the block is collapsed.
- */
-Icon.prototype.collapseHidden = true;
-
-/**
- * Height and width of icons.
- * @const
- */
-Icon.prototype.SIZE = 17;
-
-/**
- * Bubble UI (if visible).
- * @type {?Bubble}
- * @protected
- */
-Icon.prototype.bubble_ = null;
-
-/**
- * Absolute coordinate of icon's center.
- * @type {?Coordinate}
- * @protected
- */
-Icon.prototype.iconXY_ = null;
-
 /**
  * Create the icon on the block.
  */
@@ -197,7 +198,7 @@ Icon.prototype.getIconLocation = function() {
  */
 // TODO (#2562): Remove getCorrectedSize.
 Icon.prototype.getCorrectedSize = function() {
-  return new Size(Icon.prototype.SIZE, Icon.prototype.SIZE - 2);
+  return new Size(this.SIZE, this.SIZE - 2);
 };
 
 /**
diff --git a/core/mutator.js b/core/mutator.js
index bbadd41ea..d1c2ba07d 100644
--- a/core/mutator.js
+++ b/core/mutator.js
@@ -78,6 +78,30 @@ const Mutator = function(quarkNames) {
    * @private
    */
   this.workspaceHeight_ = 0;
+
+  /**
+   * The SVG element that is the parent of the mutator workspace, or null if
+   * not created.
+   * @type {?SVGSVGElement}
+   * @private
+   */
+  this.svgDialog_ = null;
+
+  /**
+   * The root block of the mutator workspace, created by decomposing the source
+   * block.
+   * @type {?BlockSvg}
+   * @private
+   */
+  this.rootBlock_ = null;
+
+  /**
+   * Function registered on the main workspace to update the mutator contents
+   * when the main workspace changes.
+   * @type {?Function}
+   * @private
+   */
+  this.sourceListener_ = null;
 };
 object.inherits(Mutator, Icon);
 
@@ -341,12 +365,12 @@ Mutator.prototype.setVisible = function(visible) {
     this.rootBlock_.moveBy(x, margin);
     // Save the initial connections, then listen for further changes.
     if (this.block_.saveConnections) {
-      const thisMutator = this;
+      const thisRootBlock = this.rootBlock_;
       const mutatorBlock =
           /** @type {{saveConnections: function(!Block)}} */ (this.block_);
       mutatorBlock.saveConnections(this.rootBlock_);
       this.sourceListener_ = function() {
-        mutatorBlock.saveConnections(thisMutator.rootBlock_);
+        mutatorBlock.saveConnections(thisRootBlock);
       };
       this.block_.workspace.addChangeListener(this.sourceListener_);
     }
diff --git a/core/warning.js b/core/warning.js
index e34e3258f..1b273bd92 100644
--- a/core/warning.js
+++ b/core/warning.js
@@ -44,6 +44,13 @@ const Warning = function(block) {
   // The text_ object can contain multiple warnings.
   this.text_ = Object.create(null);
 
+  /**
+   * The top-level node of the warning text, or null if not created.
+   * @type {?SVGTextElement}
+   * @private
+   */
+  this.paragraphElement_ = null;
+
   /**
    * Does this icon get hidden when the block is collapsed?
    * @type {boolean}