Refactor MHTMLGenerator to allow getting sending the data to a file descriptor.

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 "base/bind.h"
 #include "base/file_util.h"
@@ skipping 118 matching lines @@
     ReturnFailure(kTabClosedError);
     return;
   }
 
   web_contents->GenerateMHTML(
       mhtml_path_,
       base::Bind(&PageCaptureSaveAsMHTMLFunction::MHTMLGenerated, this));
 }
 
 void PageCaptureSaveAsMHTMLFunction::MHTMLGenerated(
-    const base::FilePath& file_path,
     int64 mhtml_file_size) {
-  DCHECK(mhtml_path_ == file_path);
   if (mhtml_file_size <= 0) {
     ReturnFailure(kMHTMLGenerationFailedError);
     return;
   }
 
   if (mhtml_file_size > std::numeric_limits<int>::max()) {
     ReturnFailure(kFileTooBigError);
     return;
   }
 
@@ skipping 39 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;
 }