Pull the Activity context from WindowAndroid if possible

ui/android/window_android.cc

Index: ui/android/window_android.cc
diff --git a/ui/android/window_android.cc b/ui/android/window_android.cc
index 5fe7779a2716b142c9818f9a3b8dde01d9d0cd9e..0ba6e6ccd121c4121766e798ea545bd36d1a0431 100644
--- a/ui/android/window_android.cc
+++ b/ui/android/window_android.cc
@@ -38,6 +38,13 @@ WindowAndroid::~WindowAndroid() {
   DCHECK(!compositor_);
 }
 
+WindowAndroid* WindowAndroid::createForTesting() {
+  JNIEnv* env = AttachCurrentThread();
+  jobject context = base::android::GetApplicationContext();
+  return new WindowAndroid(
+      env, Java_WindowAndroid_createForTesting(env, context).obj());
+}
+
 void WindowAndroid::OnCompositingDidCommit() {
   FOR_EACH_OBSERVER(WindowAndroidObserver,
                     observer_list_,