Don't scale up small browser action icons....

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 346 matching lines @@
         // 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) {
-          var canvas = document.createElement("canvas");
-          canvas.width = 19;
-          canvas.height = 19;
-        }
-
-        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() {
+          var canvas = document.createElement("canvas");
+          canvas.width = img.width > 19 ? 19 : img.width;
+          canvas.height = img.height > 19 ? 19 : img.height;
+
+          var canvas_context = canvas.getContext('2d');
           canvas_context.clearRect(0, 0, canvas.width, canvas.height);
           canvas_context.drawImage(img, 0, 0, canvas.width, canvas.height);
           delete details.path;
           details.imageData = canvas_context.getImageData(0, 0, canvas.width,
                                                           canvas.height);
           sendCustomRequest(SetExtensionActionIcon, name, [details], parameters);
         }
         img.src = details.path;
       } else {
         throw new Error(
             "Either the path or imageData property must be specified.");
       }
     }
 
     apiFunctions["browserAction.setIcon"].handleRequest = function(details) {
       setIconCommon(details, this.name, this.definition.parameters);
     };
 
     apiFunctions["pageAction.setIcon"].handleRequest = function(details) {
       setIconCommon(details, this.name, this.definition.parameters);
     };
 
     setupBrowserActionEvent(extensionId);
     setupPageActionEvents(extensionId);
     setupToolstripEvents(GetRenderViewId());
   });
 })();