Add a full Blimp integration test.

blimp/client/public/contents/blimp_contents_observer.h

Index: blimp/client/public/contents/blimp_contents_observer.h
diff --git a/blimp/client/public/contents/blimp_contents_observer.h b/blimp/client/public/contents/blimp_contents_observer.h
index 239a380fe00ea47ddf756742cfe3e0ec6452c34a..f38307ac9f47d73d8c523ffa6b7473272baa3a94 100644
--- a/blimp/client/public/contents/blimp_contents_observer.h
+++ b/blimp/client/public/contents/blimp_contents_observer.h
@@ -22,9 +22,12 @@ class BlimpContentsObserver {
   // Invoked when the navigation state of the BlimpContents has changed.
   virtual void OnNavigationStateChanged() {}
 
-  // Invoked when the BlimpContents starts or stops loading.
+  // Invoked when the BlimpContents starts or stops loading resources.
   virtual void OnLoadingStateChanged(bool loading) {}
 
+  // Invoked when the BlimpContents starts or stops loading a page.
+  virtual void OnPageLoadingStateChanged(bool loading) {}
+
   // Called by BlimpContentsDying().
   virtual void OnContentsDestroyed() {}