Remove the unnecessary construction of new services.

accessible/appview.component.js

@@ -55,10 +55,10 @@ blocklyApp.AppView = ng.core
     `,
     directives: [blocklyApp.ToolboxView, blocklyApp.WorkspaceView],
     pipes: [blocklyApp.TranslatePipe],
-    // ClipboardService declared here so that all components are using the same
-    // instance of the clipboard.
+    // The clipboard and utils services are declared here, so that all
+    // components in the application use the same instance of the service.
     // https://www.sitepoint.com/angular-2-components-providers-classes-factories-values/
-    providers: [blocklyApp.ClipboardService]
+    providers: [blocklyApp.ClipboardService, blocklyApp.UtilsService]
   })
   .Class({
     constructor: function() {}

accessible/clipboard.service.js

@@ -25,6 +25,7 @@
 blocklyApp.ClipboardService = ng.core
   .Class({
     constructor: function() {
+      blocklyApp.debug && console.log('Clipboard service constructed');
       this.clipboardBlockXml_ = null;
       this.clipboardBlockSuperiorConnection_ = null;
       this.clipboardBlockNextConnection_ = null;

accessible/fieldview.component.js

@@ -62,8 +62,7 @@ blocklyApp.FieldView = ng.core
     </li>
     `,
     inputs: ['field', 'level', 'index', 'parentId'],
-    pipes: [blocklyApp.TranslatePipe],
-    providers: [blocklyApp.TreeService, blocklyApp.UtilsService]
+    pipes: [blocklyApp.TranslatePipe]
   })
   .Class({
     constructor: [blocklyApp.UtilsService, function(_utilsService) {

accessible/toolbox_treeview.component.js

@@ -105,13 +105,14 @@ blocklyApp.ToolboxTreeView = ng.core
     }), blocklyApp.FieldView],
     inputs: [
         'block', 'displayBlockMenu', 'level', 'index', 'tree', 'noCategories'],
-    pipes: [blocklyApp.TranslatePipe],
-    providers: [blocklyApp.TreeService, blocklyApp.UtilsService]
+    pipes: [blocklyApp.TranslatePipe]
   })
   .Class({
-    constructor: [blocklyApp.ClipboardService, blocklyApp.TreeService,
-                  blocklyApp.UtilsService,
-                  function(_clipboardService, _treeService, _utilsService) {
+    constructor: [
+        blocklyApp.ClipboardService, blocklyApp.TreeService, blocklyApp.UtilsService,
+        function(_clipboardService, _treeService, _utilsService) {
+      // ClipboardService and UtilsService are app-wide singleton services.
+      // TreeService is from the parent ToolboxView component.
       this.infoBlocks = Object.create(null);
       this.clipboardService = _clipboardService;
       this.treeService = _treeService;

accessible/tree.service.js

@@ -19,6 +19,8 @@
 
 /**
  * @fileoverview Angular2 Service that handles all tree keyboard navigation.
+ * A separate TreeService is constructed for each tree in the application.
+ *
  * @author madeeha@google.com (Madeeha Ghori)
  */
 

accessible/utils.service.js

@@ -18,8 +18,10 @@
  */
 
 /**
- * @fileoverview Angular2 Service with functions required by multiple
- * components.
+ * @fileoverview Angular2 utility service for multiple components. All
+ * functions in this service should be stateless, since this is a singleton
+ * service that is used for the entire application.
+ *
  * @author madeeha@google.com (Madeeha Ghori)
  */
 
@@ -28,6 +30,7 @@ var blocklyApp = {};
 blocklyApp.UtilsService = ng.core
   .Class({
     constructor: function() {
+      blocklyApp.debug && console.log('Utils service constructed');
     },
     generateUniqueId: function() {
       return 'blockly-' + Blockly.genUid();

accessible/workspace_treeview.component.js

@@ -117,11 +117,12 @@ blocklyApp.WorkspaceTreeView = ng.core
                [level]="level">
     </tree-view>
     `,
-    directives: [ng.core.forwardRef(
-        function() { return blocklyApp.WorkspaceTreeView; }), blocklyApp.FieldView],
+    directives: [ng.core.forwardRef(function() {
+      return blocklyApp.WorkspaceTreeView;
+    }), blocklyApp.FieldView],
     inputs: ['block', 'isTopBlock', 'topBlockIndex', 'level', 'parentId'],
     pipes: [blocklyApp.TranslatePipe],
-    providers: [blocklyApp.TreeService, blocklyApp.UtilsService],
+    providers: [blocklyApp.TreeService],
   })
   .Class({
     constructor: [