Pull the Activity context from WindowAndroid if possible

ui/android/window_android.h

 // Copyright 2013 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 UI_ANDROID_WINDOW_ANDROID_H_
 #define UI_ANDROID_WINDOW_ANDROID_H_
 
 #include <jni.h>
 #include <string>
 #include <vector>
@@ skipping 51 matching lines @@
                jlong period_micros);
   void OnVisibilityChanged(JNIEnv* env, jobject obj, bool visible);
   void OnActivityStopped(JNIEnv* env, jobject obj);
   void OnActivityStarted(JNIEnv* env, jobject obj);
 
   // Return whether the specified Android permission is granted.
   bool HasPermission(const std::string& permission);
   // Return whether the specified Android permission can be requested by Chrome.
   bool CanRequestPermission(const std::string& permission);
 
+  static WindowAndroid* createForTesting();
+
  private:
   ~WindowAndroid();
 
   base::android::ScopedJavaGlobalRef<jobject> java_window_;
   gfx::Vector2dF content_offset_;
   WindowAndroidCompositor* compositor_;
 
   base::ObserverList<WindowAndroidObserver> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowAndroid);
 };
 
 }  // namespace ui
 
 #endif  // UI_ANDROID_WINDOW_ANDROID_H_