Fix potential threading issues in NetworkChangeNotifierAndroid.

net/android/network_change_notifier_android.h

Index: net/android/network_change_notifier_android.h
diff --git a/net/android/network_change_notifier_android.h b/net/android/network_change_notifier_android.h
index f5311ac9bc60abfd2f011c72797b83a9f111d0a3..2f413e4958df1fe4063b61f4def4610f31dbdffc 100644
--- a/net/android/network_change_notifier_android.h
+++ b/net/android/network_change_notifier_android.h
@@ -11,41 +11,54 @@
 #include "base/synchronization/lock.h"
 #include "net/base/network_change_notifier.h"
 
+namespace base {
+
+class TaskRunner;
+
+}  // namespace base
+
 namespace net {
 
 class NetworkChangeNotifierAndroidTest;
 
 class NetworkChangeNotifierAndroid : public NetworkChangeNotifier {
  public:
-  virtual ~NetworkChangeNotifierAndroid();
+  class Delegate {
+   public:
+    // Called from Java on the UI thread.
+    virtual void NotifyObserversOfConnectionTypeChange(
+        JNIEnv* env, jobject obj, jint new_connection_type) = 0;
 
-  // Called from Java on the UI thread.
-  void NotifyObserversOfConnectionTypeChange(
-      JNIEnv* env, jobject obj, jint new_connection_type);
-  jint GetConnectionType(JNIEnv* env, jobject obj);
+    virtual jint GetConnectionType(JNIEnv* env, jobject obj) const = 0;
+
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  virtual ~NetworkChangeNotifierAndroid();
 
   static bool Register(JNIEnv* env);
 
  private:
+  class DelegateImpl;
+
+  friend class DelegateImpl;
   friend class NetworkChangeNotifierAndroidTest;
   friend class NetworkChangeNotifierFactoryAndroid;
 
-  NetworkChangeNotifierAndroid();
+  NetworkChangeNotifierAndroid(base::TaskRunner* ui_task_runner);
 
-  void SetConnectionType(int connection_type);
+  // Wrapper used to let |Delegate| call the protected
+  // NetworkChangeNotifier::NotifyObserversOfConnectionTypeChange() method.
+  static void NotifyObservers();
 
   void ForceConnectivityState(bool state);
 
   // NetworkChangeNotifier:
   virtual ConnectionType GetCurrentConnectionType() const OVERRIDE;
 
-  base::android::ScopedJavaGlobalRef<jobject> java_network_change_notifier_;
-  // TODO(pliard): http://crbug.com/150867. Use an atomic integer for the
-  // connection type without the lock once a non-subtle atomic integer is
-  // available under base/. That might never happen though.
-  mutable base::Lock lock_;  // Protects the state below.
-  // Written from the UI thread, read from any thread.
-  int connection_type_;
+  // The delegate deletes itself.
+  DelegateImpl* const delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierAndroid);
 };