Update references to the extension messaging APIs to point to the "runtime"

chrome/test/data/extensions/api_test/filesystem_handler/tab.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.
 
 /*
 This extension is a file intent handler and does the following during the test:
 
 1. It first registers content hander.
 2. When content handler callback is invoked, opens tab.html page and passes
    file url via hash ref.
@@ skipping 28 matching lines @@
         break;
       case FileError.INVALID_STATE_ERR:
         msg = 'INVALID_STATE_ERR';
         break;
       default:
         msg = 'Unknown Error';
         break;
     };
   }
 
-  chrome.extension.sendMessage(fileBrowserExtensionId,
+  chrome.runtime.sendMessage(fileBrowserExtensionId,
                                {fileContent: null,
                                 error: {message: "File handler error: " + msg}},
                                function(response) {});
 };
 
 function onGotEntryByUrl(entry) {
   console.log('Got entry by URL: ' + entry.toURL());
   var reader = new FileReader();
   reader.onloadend = function(e) {
     if (reader.result != expectedContent) {
-      chrome.extension.sendMessage(
+      chrome.runtime.sendMessage(
           fileBrowserExtensionId,
           {fileContent: null,
            error: {message: "File content does not match."}},
           function(response) {});
     } else {
       // Send data back to the file browser extension
-      chrome.extension.sendMessage(
+      chrome.runtime.sendMessage(
           fileBrowserExtensionId,
           {fileContent: reader.result, error: null},
           function(response) {});
     }
   };
   reader.onerror = function(e) {
     errorCallback(reader.error);
   };
   entry.file(function(file) {
     reader.readAsText(file);
@@ skipping 32 matching lines @@
   reader.onerror = function(e) {
     errorCallback(reader.error);
   };
   entry.file(function(file) {
     reader.readAsText(file);
   });
 };
 
 function runFileSystemHandlerTest(entries) {
   if (!entries || entries.length != 1 || !entries[0]) {
-    chrome.extension.sendMessage(
+    chrome.runtime.sendMessage(
         fileBrowserExtensionId,
         {fileContent: null, error: "Invalid file entries."},
         function(response) {});
     return;
   }
   var entry = entries[0];
 
   // This operation should fail. If it does, we continue with testing.
   tryOpeningLogFile(entry, onLogFileOpened,
                     tryReadingReceivedFile.bind(this, entry));
@@ skipping 24 matching lines @@
 // This extension just initializes its chrome.fileBrowserHandler.onExecute
 // event listener, the real testing is done when this extension's handler is
 // invoked from filebrowser_component tests. This event will be raised from that
 // component extension test and it simulates user action in the file browser.
 // tab.html part of this extension can run only after the component raises this
 // event, since that operation sets the propery security context and creates
 // event's payload with proper file Entry instances. tab.html will return
 // results of its execution to filebrowser_component test through a
 // cross-component message.
 chrome.test.succeed();