[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/protocol/page_handler.cc

 // Copyright 2014 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 "content/browser/devtools/protocol/page_handler.h"
 
 #include <string>
 
 #include "base/base64.h"
 #include "base/bind.h"
@@ skipping 72 matching lines @@
   base::Base64Encode(
       base::StringPiece(reinterpret_cast<char*>(&data[0]), data.size()),
       &base_64_data);
 
   return base_64_data;
 }
 
 }  // namespace
 
 PageHandler::PageHandler()
-    : enabled_(false),
+    : DevToolsDomainHandler(Page::Metainfo::domainName),
+      enabled_(false),
       screencast_enabled_(false),
       screencast_quality_(kDefaultScreenshotQuality),
       screencast_max_width_(-1),
       screencast_max_height_(-1),
       capture_every_nth_frame_(1),
       capture_retry_count_(0),
       has_compositor_frame_metadata_(false),
       session_id_(0),
       frame_counter_(0),
       frames_in_flight_(0),
@@ skipping 470 matching lines @@
 Response PageHandler::StopLoading() {
   WebContentsImpl* web_contents = GetWebContents();
   if (!web_contents)
     return Response::InternalError();
   web_contents->Stop();
   return Response::OK();
 }
 
 }  // namespace protocol
 }  // namespace content