Remove one thread hop while fetching matching rules

chrome/browser/android/data_usage/external_data_use_observer_bridge.h

Index: chrome/browser/android/data_usage/external_data_use_observer_bridge.h
diff --git a/chrome/browser/android/data_usage/external_data_use_observer_bridge.h b/chrome/browser/android/data_usage/external_data_use_observer_bridge.h
index da3b8f12ce33c4ac042e210fc5322f98cc120389..bd353d3524da7e7099095132d70faae2d253e441 100644
--- a/chrome/browser/android/data_usage/external_data_use_observer_bridge.h
+++ b/chrome/browser/android/data_usage/external_data_use_observer_bridge.h
@@ -39,7 +39,7 @@ class ExternalDataUseObserver;
 class ExternalDataUseObserverBridge {
  public:
   ExternalDataUseObserverBridge();
-  ~ExternalDataUseObserverBridge();
+  virtual ~ExternalDataUseObserverBridge();
 
   // Initializes |this| on UI thread by constructing the
   // |j_external_data_use_observer_|, and fetches matching rules from
@@ -51,7 +51,7 @@ class ExternalDataUseObserverBridge {
   // Fetches matching rules from Java. Returns result asynchronously via
   // FetchMatchingRulesDone. FetchMatchingRules should not be called if a
   // fetch to matching rules is already in progress.
-  void FetchMatchingRules() const;
+  virtual void FetchMatchingRules() const;
 
   // Called by Java when new matching rules have been fetched.
   // |app_package_name| is the package name of the app that should be matched.
@@ -93,6 +93,10 @@ class ExternalDataUseObserverBridge {
                                       jobject obj,
                                       bool is_control_app_installed) const;
 
+  // Called by DataUseMatcher to notify |external_data_use_observer_| if it
+  // should register as a data use observer.
+  virtual void ShouldRegisterAsDataUseObserver(bool should_register) const;
+
  private:
   // Java listener that provides regular expressions to |this|. Data use
   // reports are submitted to |j_external_data_use_observer_|.
@@ -103,6 +107,7 @@ class ExternalDataUseObserverBridge {
   base::WeakPtr<ExternalDataUseObserver> external_data_use_observer_;
 
   // |data_use_tab_model_| is notified of the matching rules on UI thread.
+  // |data_use_tab_model_| may be null if Init has not been called yet.

[tbansal1, 2016/03/10 19:37:58]

|data_use_tab_model_| could also be null because it was destroyed (since it gets
destroyed before |this|...right?).

I think it is simpler to just  say that |data_use_tab_model_| may be null.

   base::WeakPtr<DataUseTabModel> data_use_tab_model_;
 
   // The construction time of |this|.