android: Skipping requestUnbufferedDispatch with stylus

Calling requestUnbufferedDispatch causes ANRs for some LG phones
when using a stylus on the first touch.

There's no evidence that other OEMs have this issue. If LG can fix this
bug, we don't need to make this change.

Bug: 1064161
Change-Id: I9ebfcfe4bc0e19dfa03d9b6e28cbc011ccd80561
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2243593Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Auto-Submit: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779595}

ui/android/java/src/org/chromium/ui/base/ViewAndroidDelegate.java

@@ -437,7 +437,16 @@ public class ViewAndroidDelegate {
     @TargetApi(Build.VERSION_CODES.LOLLIPOP)
     private void requestUnbufferedDispatch(MotionEvent event) {
         ViewGroup container = getContainerViewGroup();
-        if (container != null) container.requestUnbufferedDispatch(event);
+        if (container != null) {
+            for (int i = 0; i < event.getPointerCount(); i++) {
+                // This is a workaround for crbug.com/1064161.
+                // TODO(smaier) remove this if LG fixes the stylus bug.
+                if (event.getToolType(i) == MotionEvent.TOOL_TYPE_STYLUS) {
+                    return;
+                }
+            }
+            container.requestUnbufferedDispatch(event);
+        }
     }
 
     @CalledByNative