Reland "Streamline frame detach"

Source/core/frame/FrameHost.h

Index: Source/core/frame/FrameHost.h
diff --git a/Source/core/frame/FrameHost.h b/Source/core/frame/FrameHost.h
index 37dccda148597cfef4abfaba53e356e1e805a49f..aa94c51cd9f1c1262df56890b7c9cfe1dfaf1d52 100644
--- a/Source/core/frame/FrameHost.h
+++ b/Source/core/frame/FrameHost.h
@@ -82,6 +82,15 @@ public:
 
     void trace(Visitor*);
 
+    // Don't allow more than a certain number of frames in a page.
+    // This seems like a reasonable upper bound, and otherwise mutually
+    // recursive frameset pages can quickly bring the program to its knees
+    // with exponential growth in the number of frames.
+    static const int maxNumberOfFrames = 1000;
+    void incrementSubframeCount() { ++m_subframeCount; }
+    void decrementSubframeCount() { ASSERT(m_subframeCount); --m_subframeCount; }
+    int subframeCount() const;
+
 private:
     explicit FrameHost(Page&);
 
@@ -90,6 +99,7 @@ private:
     const OwnPtrWillBeMember<EventHandlerRegistry> m_eventHandlerRegistry;
 
     AtomicString m_overrideEncoding;
+    int m_subframeCount;
 };
 
 }