Extract minimal RenderViewHost interface for embedders, leaving

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index d36c2d583cf7dd2182ef60ddc658634c910f01ee..c9d0df5a9fee58ed7893b7d4e0882fc3dbc9fb0e 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -119,7 +119,8 @@ class RenderWidgetHostViewAura::WindowObserver : public aura::WindowObserver {
 // RenderWidgetHostViewAura, public:
 
 RenderWidgetHostViewAura::RenderWidgetHostViewAura(RenderWidgetHost* host)
-    : ALLOW_THIS_IN_INITIALIZER_LIST(window_(new aura::Window(this))),
+    : host_(RenderWidgetHostImpl::From(host)),
+      ALLOW_THIS_IN_INITIALIZER_LIST(window_(new aura::Window(this))),
       is_fullscreen_(false),
       popup_parent_host_view_(NULL),
       popup_child_host_view_(NULL),
@@ -130,7 +131,6 @@ RenderWidgetHostViewAura::RenderWidgetHostViewAura(RenderWidgetHost* host)
       current_surface_(0),
       paint_canvas_(NULL),
       synthetic_move_sent_(false) {
-  host_ = static_cast<RenderWidgetHostImpl*>(host);
   host_->SetView(this);
   window_observer_.reset(new WindowObserver(this));
   window_->AddObserver(window_observer_.get());