Adding a way to associate Android Activities with PlatformWindowAndroid

ui/platform_window/android/platform_window_android.h

Index: ui/platform_window/android/platform_window_android.h
diff --git a/ui/platform_window/android/platform_window_android.h b/ui/platform_window/android/platform_window_android.h
index c8c646ebcdd265a6dff943fe57701d06c74e687c..21ce7eed92753ac95a3f1139a000ff265957080f 100644
--- a/ui/platform_window/android/platform_window_android.h
+++ b/ui/platform_window/android/platform_window_android.h
@@ -23,10 +23,14 @@ namespace ui {
 class ANDROID_WINDOW_EXPORT PlatformWindowAndroid : public PlatformWindow {
  public:
   static bool Register(JNIEnv* env);
+  static PlatformWindowAndroid* From(PlatformWindow* platform_window);
 
   explicit PlatformWindowAndroid(PlatformWindowDelegate* delegate);
   ~PlatformWindowAndroid() override;
 
+  void AttachToActivity(JNIEnv* env,
+                        const base::android::JavaRef<jobject>& activity);
+  bool IsAttachedToActivity() const;
   void Destroy(JNIEnv* env, jobject obj);
   void SurfaceCreated(JNIEnv* env,
                       jobject obj,