Check null java object when request vsync

ui/android/window_android.cc

 // 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.
 
 #include "ui/android/window_android.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_weak_ref.h"
 #include "base/android/scoped_java_ref.h"
@@ skipping 54 matching lines @@
 void WindowAndroid::DetachCompositor() {
   compositor_ = NULL;
   FOR_EACH_OBSERVER(WindowAndroidObserver,
                     observer_list_,
                     OnDetachCompositor());
   observer_list_.Clear();
 }
 
 void WindowAndroid::RequestVSyncUpdate() {
   JNIEnv* env = AttachCurrentThread();
-  Java_WindowAndroid_requestVSyncUpdate(env, GetJavaObject().obj());
+  ScopedJavaLocalRef<jobject> obj = GetJavaObject();
+  if (obj.is_null())
+    return;
+  Java_WindowAndroid_requestVSyncUpdate(env, obj.obj());
 }
 
 void WindowAndroid::SetNeedsAnimate() {
   if (compositor_)
     compositor_->SetNeedsAnimate();
 }
 
 void WindowAndroid::Animate(base::TimeTicks begin_frame_time) {
   FOR_EACH_OBSERVER(
       WindowAndroidObserver, observer_list_, OnAnimate(begin_frame_time));
@@ skipping 17 matching lines @@
 // ----------------------------------------------------------------------------
 // Native JNI methods
 // ----------------------------------------------------------------------------
 
 jlong Init(JNIEnv* env, jobject obj) {
   WindowAndroid* window = new WindowAndroid(env, obj);
   return reinterpret_cast<intptr_t>(window);
 }
 
 }  // namespace ui