Block onScroll if input MotionEvents are null

chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/eventfilter/GestureEventFilter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/eventfilter/GestureEventFilter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/eventfilter/GestureEventFilter.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/eventfilter/GestureEventFilter.java
index cfde807b5878a3d675208a9f8a865086f45ff508..5353df4ad6d7b08ae01dc7d0adee01e66122659c 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/eventfilter/GestureEventFilter.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/eventfilter/GestureEventFilter.java
@@ -98,6 +98,10 @@ public class GestureEventFilter extends EventFilter {
             @Override
             public boolean onScroll(MotionEvent e1, MotionEvent e2,
                     float distanceX, float distanceY) {
+                // This should ideally never happen but is used as a workaround for a larger
+                // problem. See https://crbug.com/656603
+                if (e1 == null || e2 == null) return false;
+
                 if (!mSeenFirstScrollEvent) {
                     // Remove the touch slop region from the first scroll event to avoid a
                     // jump.