Pull the Activity context from WindowAndroid if possible

ui/android/window_android.h

Index: ui/android/window_android.h
diff --git a/ui/android/window_android.h b/ui/android/window_android.h
index 58f1e280bd6a9639ac9368cce647ed9a1ef2c86b..f08b2f2a5300629aaaa803fc99e9ade213054381 100644
--- a/ui/android/window_android.h
+++ b/ui/android/window_android.h
@@ -69,6 +69,8 @@ class UI_ANDROID_EXPORT WindowAndroid {
   // Return whether the specified Android permission can be requested by Chrome.
   bool CanRequestPermission(const std::string& permission);
 
+  static WindowAndroid* createForTesting();
+
  private:
   ~WindowAndroid();