Avoid AddRef'ing non-thread-safe ref count on PageCaptureSaveAsMHTML

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 <limits>
 #include <memory>
 
 #include "base/bind.h"
@@ skipping 19 matching lines @@
 
 namespace SaveAsMHTML = extensions::api::page_capture::SaveAsMHTML;
 
 namespace {
 
 const char kFileTooBigError[] = "The MHTML file generated is too big.";
 const char kMHTMLGenerationFailedError[] = "Failed to generate MHTML.";
 const char kTemporaryFileError[] = "Failed to create a temporary file.";
 const char kTabClosedError[] = "Cannot find the tab for this request.";
 
+void ClearFileReferenceOnIOThread(
+    scoped_refptr<storage::ShareableFileReference>) {}
+
 }  // namespace
 
 static PageCaptureSaveAsMHTMLFunction::TestDelegate* test_delegate_ = NULL;
 
 PageCaptureSaveAsMHTMLFunction::PageCaptureSaveAsMHTMLFunction() {
 }
 
 PageCaptureSaveAsMHTMLFunction::~PageCaptureSaveAsMHTMLFunction() {
   if (mhtml_file_.get()) {
-    storage::ShareableFileReference* to_release = mhtml_file_.get();
-    to_release->AddRef();
-    mhtml_file_ = NULL;
-    BrowserThread::ReleaseSoon(BrowserThread::IO, FROM_HERE, to_release);
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(&ClearFileReferenceOnIOThread, base::Passed(&mhtml_file_)));
   }
 }
 
 void PageCaptureSaveAsMHTMLFunction::SetTestDelegate(TestDelegate* delegate) {
   test_delegate_ = delegate;
 }
 
 bool PageCaptureSaveAsMHTMLFunction::RunAsync() {
   params_ = SaveAsMHTML::Params::Create(*args_);
   EXTENSION_FUNCTION_VALIDATE(params_.get());
@@ skipping 130 matching lines @@
                                     GetProfile(),
                                     include_incognito(),
                                     &browser,
                                     NULL,
                                     &web_contents,
                                     NULL)) {
     return NULL;
   }
   return web_contents;
 }