Introduce content::RenderWidgetHostViewPort (in content/port/browser).

content/browser/renderer_host/render_widget_host.h

Index: content/browser/renderer_host/render_widget_host.h
diff --git a/content/browser/renderer_host/render_widget_host.h b/content/browser/renderer_host/render_widget_host.h
index 46b0b83dc395c6e9b6e3de4e3df1b3189c3525b9..e6f473841a0c521156a41f1a83ccd1da5b4e5c7f 100644
--- a/content/browser/renderer_host/render_widget_host.h
+++ b/content/browser/renderer_host/render_widget_host.h
@@ -32,7 +32,6 @@
 class BackingStore;
 struct EditCommand;
 class RenderWidgetHostView;
-class RenderWidgetHostViewBase;
 class TransportDIB;
 struct ViewHostMsg_UpdateRect_Params;
 class WebCursor;
@@ -43,6 +42,7 @@ class TimeTicks;
 
 namespace content {
 class RenderProcessHost;
+class RenderWidgetHostViewPort;
 }
 
 namespace gfx {
@@ -546,7 +546,7 @@ class CONTENT_EXPORT RenderWidgetHost : public IPC::Channel::Listener,
   // crashes, its View is destroyed and this pointer becomes NULL, even though
   // render_view_host_ lives on to load another URL (creating a new View while
   // doing so).
-  RenderWidgetHostViewBase* view_;
+  content::RenderWidgetHostViewPort* view_;
 
   // true if a renderer has once been valid. We use this flag to display a sad
   // tab only when we lose our renderer and not if a paint occurs during