Fix requestUnbufferedDispatch didn't work before window attached

Before window attached to view, the parent of root view would be null
cause the unbuffered request can't be updated to the `ViewRootImpl`.

This will update the unbuffered request when the root view set to its
`ViewRootImpl`, so we could make sure the unbuffered request could be
consistent in root view and its ViewRootImpl.

Bug: 268105812
Test: manual
Change-Id: Ifd9cf0969229daeac73f8fb95c6a9fe8c81a985f

core/java/android/view/ViewRootImpl.java

@@ -1391,6 +1391,8 @@ public final class ViewRootImpl implements ViewParent,
                                 listener, listener.data, mHandler, true /*waitForPresentTime*/);
                         mAttachInfo.mThreadedRenderer.addObserver(mHardwareRendererObserver);
                     }
+                    // Update unbuffered request when set the root view.
+                    mUnbufferedInputSource = mView.mUnbufferedInputSource;
                 }
 
                 view.assignParent(this);