Migrate TabControlFeature from 0.5 to 0.6

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 dc3e1ec892ab03b6ee1fe4453337a05608e487b9..97ba59535af46d5ba555d4ab03bfbba8573ac181 100644
--- a/blimp/client/public/contents/blimp_contents_observer.h
+++ b/blimp/client/public/contents/blimp_contents_observer.h
@@ -15,15 +15,26 @@ namespace client {
 // related to BlimpContents.
 class BlimpContentsObserver {
  public:
-  virtual ~BlimpContentsObserver() = default;
+  virtual ~BlimpContentsObserver();
 
   // Invoked when the navigation state of the BlimpContents has changed.
   virtual void OnNavigationStateChanged() {}
 
+  // Invoked when the blimp contents is destroyed.
+  virtual void OnContentsDestroyed();
+
+  BlimpContents* blimp_contents() { return contents_; }
+
  protected:
-  BlimpContentsObserver() {}
+  explicit BlimpContentsObserver(BlimpContents* blimp_contents);
+
+  // Can be used by subclass to clear the contents_ to nullptr.
+  void ClearBlimpContents();

[David Trainor- moved to gerrit, 2016/08/06 04:32:58]

See above, now that I think about it this should happen all in the base class
and not require any overriding by the subclasses.

[Menglin, 2016/08/09 00:31:18]

Done.

 
  private:
+  // The BlimpContents being tracked by this BlimpContentsObserver.
+  BlimpContents* contents_;
+
   DISALLOW_COPY_AND_ASSIGN(BlimpContentsObserver);
 };