Remove scoped_refptr::release which is confusing and causes leaks.

chrome/browser/extensions/api/page_capture/page_capture_api.cc

 // 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.
 
 #include "chrome/browser/extensions/api/page_capture/page_capture_api.h"
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
@@ skipping 26 matching lines @@
 
 }  // namespace
 
 static PageCaptureSaveAsMHTMLFunction::TestDelegate* test_delegate_ = NULL;
 
 PageCaptureSaveAsMHTMLFunction::PageCaptureSaveAsMHTMLFunction() {
 }
 
 PageCaptureSaveAsMHTMLFunction::~PageCaptureSaveAsMHTMLFunction() {
   if (mhtml_file_.get()) {
+    mhtml_file_->AddRef();
     BrowserThread::ReleaseSoon(BrowserThread::IO, FROM_HERE,
-                               mhtml_file_.release());
+                               mhtml_file_.get());

[michaeln, 2012/12/06 00:26:12]

This pattern is buggy.

You should also clear out the ref held in mhtml_file_ prior to invoking
ReleaseSoon. That release task may run on the target thread prior to this thread
making progress. When that happens the final release will occur on the wrong
thread.

[piman, 2012/12/06 04:56:27]

You're right, done. I verified that the other changes are not subject to this
caveat (mostly because they call release on a local variable, that isn't visible
from other threads).

Note however that the new version, no more and no less than the new version, has
any way to ensure that some other thing (e.g. a posted task) doesn't have a
separate reference to that object.

   }
 }
 
 void PageCaptureSaveAsMHTMLFunction::SetTestDelegate(TestDelegate* delegate) {
   test_delegate_ = delegate;
 }
 
 bool PageCaptureSaveAsMHTMLFunction::RunImpl() {
   params_ = SaveAsMHTML::Params::Create(*args_);
   EXTENSION_FUNCTION_VALIDATE(params_.get());
@@ skipping 128 matching lines @@
   Browser* browser = NULL;
   content::WebContents* web_contents = NULL;
 
   if (!ExtensionTabUtil::GetTabById(params_->details.tab_id, profile(),
                                     include_incognito(), &browser, NULL,
                                     &web_contents, NULL)) {
     return NULL;
   }
   return web_contents;
 }