Remove one thread hop while fetching matching rules

chrome/browser/android/data_usage/external_data_use_observer_bridge.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ANDROID_DATA_USAGE_EXTERNAL_DATA_USE_OBSERVER_BRIDGE_H_
 #define CHROME_BROWSER_ANDROID_DATA_USAGE_EXTERNAL_DATA_USE_OBSERVER_BRIDGE_H_
 
 #include <jni.h>
 #include <stdint.h>
 
@@ skipping 21 matching lines @@
 class ExternalDataUseObserver;
 
 // ExternalDataUseObserverBridge creates and owns a Java listener object
 // that is notified of the data usage observations of Chromium. This class
 // receives regular expressions from the Java listener object. Objects of this
 // class may may be constructed on any thread safe but are immediately moved to
 // the UI thread, and afterwards are accessible only on the UI thread.
 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
   // |j_external_data_use_observer_|.
   void Init(scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
             base::WeakPtr<ExternalDataUseObserver> external_data_use_observer,
             DataUseTabModel* data_use_tab_model);
 
   // 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.
   // |domain_path_regex| is the regex to be used for matching URLs. |label| is
   // the label that must be applied to data reports corresponding to the
   // matching rule, and must uniquely identify the matching rule. Each element
   // in |label| must have non-zero length. The three vectors should have equal
   // length. The vectors may be empty which implies that no matching rules are
   // active.
   void FetchMatchingRulesDone(
@@ skipping 21 matching lines @@
                            const base::android::JavaParamRef<jobject>& obj,
                            bool success);
 
   // Notifies the ExternalDataUseObserverBridge that the external control app is
   // installed or uninstalled. |is_control_app_installed| is true if app is
   // installed.
   void OnControlAppInstallStateChange(JNIEnv* env,
                                       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_|.
   base::android::ScopedJavaGlobalRef<jobject> j_external_data_use_observer_;
 
   // |external_data_use_observer_| owns |this|. |external_data_use_observer_| is
   // notified of results from Java code by |this|.
   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|.
   const base::TimeTicks construct_time_;
 
   // True if matching rules are fetched for the first time.
   bool is_first_matching_rule_fetch_;
 
   // |io_task_runner_| accesses ExternalDataUseObserver members on IO thread.
   scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalDataUseObserverBridge);
 };
 
 bool RegisterExternalDataUseObserver(JNIEnv* env);
 
 }  // namespace android
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_ANDROID_DATA_USAGE_EXTERNAL_DATA_USE_OBSERVER_BRIDGE_H_