Reland #1 of: Move WebUI ownership from the RenderFrameHostManager to the RenderFrameHost.

content/browser/webui/web_ui_impl.h

Index: content/browser/webui/web_ui_impl.h
diff --git a/content/browser/webui/web_ui_impl.h b/content/browser/webui/web_ui_impl.h
index 86c70711282a2ec7c9e7aa78d9954b27387c7f57..3a50235bf1ebe5288e6c273c9e3eb6e371515c8e 100644
--- a/content/browser/webui/web_ui_impl.h
+++ b/content/browser/webui/web_ui_impl.h
@@ -25,13 +25,13 @@ class CONTENT_EXPORT WebUIImpl : public WebUI,
   WebUIImpl(WebContents* contents, const std::string& frame_name);
   ~WebUIImpl() override;
 
-  // Called by WebContentsImpl when the RenderView is first created. This is
-  // *not* called for every page load because in some cases
-  // RenderFrameHostManager will reuse RenderView instances.
+  // Should be called whenever a navigation causes a change in the
+  // WebUI/RenderView pair of instances: a WebUI is created for an existing
+  // RenderView, vice-versa or if both have just been created.
   void RenderViewCreated(RenderViewHost* render_view_host);
 
-  // Called by WebContentsImpl when the RenderView is reused. This happens on
-  // refresh or when the main page is navigated within the same SiteInstance.
+  // Should be called when a navigation reuses the exact same WebUI/RenderView
+  // pair of instances.
   void RenderViewReused(RenderViewHost* render_view_host, bool was_main_frame);
 
   // WebUI implementation: