Reland "Streamline frame detach"

Source/core/frame/Frame.h

Index: Source/core/frame/Frame.h
diff --git a/Source/core/frame/Frame.h b/Source/core/frame/Frame.h
index 91bc33e62168014b665c4b61b224f4eacbc55e9d..23cadf45d42d2a33e32eb13ae2e6dbad7bf672e4 100644
--- a/Source/core/frame/Frame.h
+++ b/Source/core/frame/Frame.h
@@ -59,11 +59,10 @@ public:
     virtual void trace(Visitor*);
 
     virtual void navigate(Document& originDocument, const KURL&, bool lockBackForwardList) = 0;
-    virtual void detach() = 0;
+    virtual void detach();
     void detachChildren();
 
     FrameClient* client() const;
-    void clearClient();
 
     // NOTE: Page is moving out of Blink up into the browser process as
     // part of the site-isolation (out of process iframes) work.
@@ -121,11 +120,6 @@ inline FrameClient* Frame::client() const
     return m_client;
 }
 
-inline void Frame::clearClient()
-{
-    m_client = 0;
-}
-
 inline LocalDOMWindow* Frame::domWindow() const
 {
     return m_domWindow.get();