Delete the temporary file when generating MHTML with the extension API.

chrome/test/data/extensions/api_test/save_page/test.js

 // Copyright (c) 2011 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.
 
 // API test for chrome.extension.savePage.
 // browser_tests.exe --gtest_filter=ExtensionApiTest.SavePage
 
 const assertEq = chrome.test.assertEq;
 const assertTrue = chrome.test.assertTrue;
 
@@ skipping 22 matching lines @@
             assertEq(undefined, chrome.extension.lastError);
             assertTrue(data != null);
             // It should contain few KBs of data.
             assertTrue(data.size > 100);
             // Let's make sure it contains some well known strings.
             var reader = new FileReader();
             reader.onload = function(e) {
               var text = e.target.result;
               assertTrue(text.indexOf(testUrl) != -1);
               assertTrue(text.indexOf("logo.png") != -1);
-              chrome.test.notifyPass();
+              // Run the GC so the blob is deleted.
+              window.setTimeout(function() { window.gc(); });
+              window.setTimeout(function() { chrome.test.notifyPass(); }, 0);
             };
             reader.readAsText(data);
           });
         });
       });
     }
   ]);
 });