Warn developers about deprecated features only once per page-load.

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 5a0c485f698465174ccdcdeb0d901125e95ca4ef..472082858cb815801c4b00572a38a3d645f3a37c 100644
--- a/Source/core/page/Page.h
+++ b/Source/core/page/Page.h
@@ -21,7 +21,7 @@
 #ifndef Page_h
 #define Page_h
 
-#include "UseCounter.h"
+#include "DeprecationAgent.h"
 #include "FindOptions.h"
 #include "FrameLoaderTypes.h"
 #include "LayoutMilestones.h"
@@ -31,6 +31,7 @@
 #include "PlatformScreen.h"
 #include "Region.h"
 #include "Supplementable.h"
+#include "UseCounter.h"
 #include "ViewportArguments.h"
 #include <wtf/Forward.h>
 #include <wtf/HashMap.h>
@@ -53,6 +54,7 @@ class ClientRectList;
 class ContextMenuClient;
 class ContextMenuController;
 class Document;
+class DeprecationAgent;
 class DragCaretController;
 class DragClient;
 class DragController;
@@ -189,6 +191,8 @@ public:
 
     UseCounter* useCounter() { return &m_UseCounter; }
 
+    DeprecationAgent* deprecationAgent() { return &m_deprecationAgent; }
+
     enum ViewMode {
         ViewModeInvalid,
         ViewModeWindowed,
@@ -374,6 +378,8 @@ private:
 
     UseCounter m_UseCounter;
 
+    DeprecationAgent m_deprecationAgent;
+
     int m_subframeCount;
     String m_groupName;
     bool m_openedByDOM;