Check for view nullptr to prevent a crash

Bug: 1045954
Change-Id: I1a52383a4b3240fdb87d93e07dd312385bca0156
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2071285Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Commit-Queue: Navid Zolghadr <nzolghadr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744838}

content/browser/renderer_host/render_widget_host_input_event_router.cc

@@ -167,8 +167,8 @@ void TouchEventAckQueue::MarkAcked(const TouchEventWithLatencyInfo& touch_event,
     // If the touch-event was sent directly to the view without going through
     // RenderWidgetHostInputEventRouter, as is the case with AndroidWebView,
     // then we must ack it directly.
-    DCHECK(target_view);
-    target_view->ProcessAckedTouchEvent(touch_event, ack_result);
+    if (target_view)
+      target_view->ProcessAckedTouchEvent(touch_event, ack_result);
     return;
   }