Refactor implementation of BrowserActions, and add support for

chrome/renderer/resources/extension_process_bindings.js

 // Copyright (c) 2009 The chrome Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This script contains privileged chrome extension related javascript APIs.
 // It is loaded by pages whose URL has the chrome-extension protocol.
 
 var chrome = chrome || {};
 (function() {
   native function GetExtensionAPIDefinition();
@@ skipping 315 matching lines @@
         tabIdProxy[name] = new chrome.Event("devtools." + tabId + "." + name);
       });
       return tabIdProxy;
     }
 
     apiFunctions["i18n.getMessage"].handleRequest =
         function(message_name, placeholders) {
       return GetL10nMessage(message_name, placeholders);
     }
 
-    var canvas_context;
+    var canvas;
     function setIconCommon(details, name, parameters) {
       if ("iconIndex" in details) {
         sendRequest(name, [details], parameters);
       } else if ("imageData" in details) {
         // Verify that this at least looks like an ImageData element.
         // Unfortunately, we cannot use instanceof because the ImageData
         // constructor is not public.
         //
         // We do this manually instead of using JSONSchema to avoid having these
         // properties show up in the doc.
         if (!("width" in details.imageData) ||
             !("height" in details.imageData) ||
             !("data" in details.imageData)) {
           throw new Error(
               "The imageData property must contain an ImageData object.");
         }
         sendCustomRequest(SetExtensionActionIcon, name, [details], parameters);
       } else if ("path" in details) {
-        if (!canvas_context) {
+        if (!canvas) {
           var canvas = document.createElement("canvas");
           canvas.width = 19;
           canvas.height = 19;
-          canvas_context = canvas.getContext('2d');
         }
 
+        var canvas_context = canvas.getContext('2d');
         var img = new Image();
         var self = this;
         img.onerror = function() {
           console.error("Could not load browser action icon '" + details.path +
                         "'.");
         }
         img.onload = function() {
           canvas_context.clearRect(0, 0, canvas.width, canvas.height);
           canvas_context.drawImage(img, 0, 0, canvas.width, canvas.height);
           delete details.path;
@@ skipping 14 matching lines @@
 
     apiFunctions["pageAction.setIcon"].handleRequest = function(details) {
       setIconCommon(details, this.name, this.definition.parameters);
     };
 
     setupBrowserActionEvent(extensionId);
     setupPageActionEvents(extensionId);
     setupToolstripEvents(GetRenderViewId());
   });
 })();