Make start/stop loading notifications per-frame

Source/core/page/Page.h

Index: Source/core/page/Page.h
diff --git a/Source/core/page/Page.h b/Source/core/page/Page.h
index c25fa8d6b31d8fc55ce3417679c6b3158e195ca8..7248f896cdda0553437183aaccddba16f8fc5dfa 100644
--- a/Source/core/page/Page.h
+++ b/Source/core/page/Page.h
@@ -63,7 +63,6 @@ class PageLifecycleNotifier;
 class PlatformMouseEvent;
 class PluginData;
 class PointerLockController;
-class ProgressTracker;
 class Range;
 class RenderBox;
 class RenderObject;
@@ -161,7 +160,6 @@ public:
     PassRefPtr<ClientRectList> nonFastScrollableRects(const LocalFrame*);
 
     Settings& settings() const { return *m_settings; }
-    ProgressTracker& progress() const { return *m_progress; }
     BackForwardClient& backForward() const { return *m_backForwardClient; }
 
     UseCounter& useCounter() { return m_useCounter; }
@@ -252,7 +250,6 @@ private:
     OwnPtr<ScrollingCoordinator> m_scrollingCoordinator;
 
     const OwnPtr<HistoryController> m_historyController;
-    const OwnPtr<ProgressTracker> m_progress;
     const OwnPtr<UndoStack> m_undoStack;
 
     RefPtr<LocalFrame> m_mainFrame;