Add CobaltRenderFrameObserver comments, style fix

cobalt/renderer/cobalt_render_frame_observer.cc

@@ -32,8 +32,12 @@ void CobaltRenderFrameObserver::OnDestruct() {
 }
 
 void CobaltRenderFrameObserver::DidClearWindowObject() {
-  auto& cmd = *base::CommandLine::ForCurrentProcess();
+  const auto& cmd = *base::CommandLine::ForCurrentProcess();
   if (cmd.HasSwitch(switches::kExposeInternalsForTesting)) {
+    // The internals object is injected here so that window.internals is exposed
+    // to JavaScript at initial load of the web app, when the frame navigates
+    // from the initial empty document to the actual document. This approach is
+    // borrowed from content shell.
     blink::WebTestingSupport::InjectInternalsObject(
         render_frame()->GetWebFrame());
   }

cobalt/renderer/cobalt_render_frame_observer.h

@@ -20,6 +20,7 @@
 
 namespace cobalt {
 
+// Enables Cobalt-specific responses to notifications of changes to the frame.
 class CobaltRenderFrameObserver : public content::RenderFrameObserver {
  public:
   explicit CobaltRenderFrameObserver(content::RenderFrame* render_frame);
@@ -30,7 +31,14 @@ class CobaltRenderFrameObserver : public content::RenderFrameObserver {
       delete;
 
  private:
+  // content::RenderFrameObserver impl.
+
+  // Overridden so that the observer has the same lifetime as the RenderFrame.
   void OnDestruct() override;
+
+  // Overridden for Cobalt-specific responses to this particular notification.
+  // See blink::WebLocalFrameClient.DidClearWindowObject() for details about
+  // when it's sent.
   void DidClearWindowObject() override;
 };