Inside of content, prefer SiteInstanceImpl to SiteInstance.

content/browser/frame_host/render_frame_proxy_host.h

Index: content/browser/frame_host/render_frame_proxy_host.h
diff --git a/content/browser/frame_host/render_frame_proxy_host.h b/content/browser/frame_host/render_frame_proxy_host.h
index 6aa2848c3c7a43e7381f390c7a85e1386e25a750..61758c4d72fe4869aa8551b42b44a5ca6e6cb755 100644
--- a/content/browser/frame_host/render_frame_proxy_host.h
+++ b/content/browser/frame_host/render_frame_proxy_host.h
@@ -63,7 +63,7 @@ class RenderFrameProxyHost
  public:
   static RenderFrameProxyHost* FromID(int process_id, int routing_id);
 
-  RenderFrameProxyHost(SiteInstance* site_instance,
+  RenderFrameProxyHost(SiteInstanceImpl* site_instance,
                        RenderViewHostImpl* render_view_host,
                        FrameTreeNode* frame_tree_node);
   ~RenderFrameProxyHost() override;
@@ -80,9 +80,7 @@ class RenderFrameProxyHost
     return routing_id_;
   }
 
-  SiteInstance* GetSiteInstance() {
-    return site_instance_.get();
-  }
+  SiteInstanceImpl* GetSiteInstance() { return site_instance_.get(); }
 
   FrameTreeNode* frame_tree_node() const { return frame_tree_node_; };
 
@@ -135,8 +133,8 @@ class RenderFrameProxyHost
   // This RenderFrameProxyHost's routing id.
   int routing_id_;
 
-  // The SiteInstance this proxy is associated with.
-  scoped_refptr<SiteInstance> site_instance_;
+  // The SiteInstanceImpl this proxy is associated with.
+  scoped_refptr<SiteInstanceImpl> site_instance_;
 
   // The renderer process this RenderFrameHostProxy is associated with. It is
   // equivalent to the result of site_instance_->GetProcess(), but that