Lazy load chrome.* APIs

chrome/renderer/resources/extensions/last_error.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-requireNative('runtime');
+var DCHECK = requireNative('logging').DCHECK;
+var GetAvailability = requireNative('v8_context').GetAvailability;
+var GetGlobal = requireNative('sendRequest').GetGlobal;
 
-function set(message) {
+// Utility for setting chrome.*.lastError.
+//
+// A utility here is useful for two reasons:
+//  1. For backwards compatibility we need to set chrome.extension.lastError,
+//     but not all contexts actually have access to the extension namespace.
+//  2. When calling across contexts, the global object that gets lastError set
+//     needs to be that of the caller. We force callers to explicitly specify
+//     the chrome object to try to prevent bugs here.
+
+/**
+ * Sets the last error on |targetChrome| to |message|.
+ */
+function set(message, targetChrome) {
+  DCHECK(targetChrome != undefined);
+  clear(targetChrome);  // in case somebody has set a sneaky getter/setter
   var errorObject = { 'message': message };
-  if (chrome.extension)
-    chrome.extension.lastError = errorObject;
-  chrome.runtime.lastError = errorObject;
+  if (GetAvailability('extension').is_available)
+    targetChrome.extension.lastError = errorObject;
+  targetChrome.runtime.lastError = errorObject;
 };
 
-function clear() {
-  if (chrome.extension)
-    delete chrome.extension.lastError;
-  delete chrome.runtime.lastError;
+/**
+ * Clears the last error on |targetChrome|.
+ */
+function clear(targetChrome) {
+  DCHECK(targetChrome != undefined);
+  if (GetAvailability('extension').is_available)
+    delete targetChrome.extension.lastError;
+  delete targetChrome.runtime.lastError;
 };
 
+/**
+ * Runs |callback(args)| with last error set to |message|.
+ *
+ * The target chrome object is the global object's of the callback, so this
+ * method won't work if the real callback has been wrapped (etc).
+ */
+function run(message, callback, args) {
+  var targetChrome = GetGlobal(callback).chrome;
+  set(message, targetChrome);
+  try {
+    callback.apply(undefined, args);
+  } finally {
+    clear(targetChrome);
+  }
+}
+
 exports.clear = clear;
 exports.set = set;
+exports.run = run;