[WebView] Add unique visual state request ids.

android_webview/native/aw_contents.h

Index: android_webview/native/aw_contents.h
diff --git a/android_webview/native/aw_contents.h b/android_webview/native/aw_contents.h
index 077690fcbccb915cf444a04420184e6f11def1d5..d02c39a189dec6f34b66f8ca69183221b5d1b1ec 100644
--- a/android_webview/native/aw_contents.h
+++ b/android_webview/native/aw_contents.h
@@ -129,7 +129,10 @@ class AwContents : public FindHelper::Listener,
   jlong GetAwDrawGLViewContext(JNIEnv* env, jobject obj);
   jlong CapturePicture(JNIEnv* env, jobject obj, int width, int height);
   void EnableOnNewPicture(JNIEnv* env, jobject obj, jboolean enabled);
-  void FlushVisualState(JNIEnv* env, jobject obj, jobject callback);
+  void FlushVisualState(JNIEnv* env,
+                        jobject obj,
+                        jobject callback,
+                        int64 request_id);
   void ClearView(JNIEnv* env, jobject obj);
   void SetExtraHeadersForUrl(JNIEnv* env, jobject obj,
                              jstring url, jstring extra_headers);