Migrate PingLoader to be a LocalFrameLifecycleObserver.

Source/core/html/HTMLAnchorElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  * Copyright (C) 2003, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 11 matching lines @@
  */
 
 #include "config.h"
 #include "core/html/HTMLAnchorElement.h"
 
 #include "bindings/core/v8/V8DOMActivityLogger.h"
 #include "core/events/KeyboardEvent.h"
 #include "core/events/MouseEvent.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/Settings.h"
+#include "core/frame/UseCounter.h"

[Nate Chapin, 2015/08/31 23:50:15]

Why?

[ncarter (slow), 2015/09/01 21:10:56]

Without the new #include we'd get a compile error on line 326.

It used to be pulled in via core/loader/PingLoader.h ->
core/page/PageLifecycleObserver.h -> core/page/Page.h -> core/frame/UseCounter.h

Now PingLoader.h no longer pulls in PageLifecycleObserver.h, and UseCounter.h is
not pulled in by any of the other transitive includes of this translation unit, 

 #include "core/html/HTMLImageElement.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/layout/LayoutImage.h"
 #include "core/loader/FrameLoadRequest.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/loader/PingLoader.h"
 #include "core/page/ChromeClient.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/network/NetworkHints.h"
 #include "platform/weborigin/SecurityPolicy.h"
@@ skipping 358 matching lines @@
             Vector<String> argv;
             argv.append("a");
             argv.append(fastGetAttribute(hrefAttr));
             activityLogger->logEvent("blinkAddElement", argv.size(), argv.data());
         }
     }
     return HTMLElement::insertedInto(insertionPoint);
 }
 
 } // namespace blink