Prevent touchscreen pinch events from being sent to child renderers

If we pinch an element with a touch-action that prevents pinch in an
OOPIF, we route the pinch events to the child so that the child's
TouchActionFilter filters them. Due to crbug.com/771330, the
TouchActionFilter could let the pinch events through. We'll
filter such events in RenderWidgetHostViewChildFrame::FilterInputEvent
to prevent them from being sent to the child renderer.

Bug: 827182
Change-Id: I3782a2d135a008df271a73d79ecade25dcc9f1a5
Reviewed-on: https://chromium-review.googlesource.com/1040354Reviewed-by: James MacLean <wjmaclean@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555743}

content/browser/renderer_host/render_widget_host_view_child_frame.cc

@@ -956,6 +956,19 @@ void RenderWidgetHostViewChildFrame::TakeFallbackContentFrom(
 
 InputEventAckState RenderWidgetHostViewChildFrame::FilterInputEvent(
     const blink::WebInputEvent& input_event) {
+  // A child renderer should not receive touchscreen pinch events. Ideally, we
+  // would DCHECK this, but since touchscreen pinch events may be targeted to
+  // a child in order to have the child's TouchActionFilter filter them, we
+  // may encounter https://crbug.com/771330 which would let the pinch events
+  // through.
+  if (blink::WebInputEvent::IsPinchGestureEventType(input_event.GetType())) {
+    const blink::WebGestureEvent& gesture_event =
+        static_cast<const blink::WebGestureEvent&>(input_event);
+    if (gesture_event.SourceDevice() == blink::kWebGestureDeviceTouchscreen) {
+      return INPUT_EVENT_ACK_STATE_CONSUMED;
+    }
+  }
+
   if (input_event.GetType() == blink::WebInputEvent::kGestureFlingStart) {
     const blink::WebGestureEvent& gesture_event =
         static_cast<const blink::WebGestureEvent&>(input_event);

content/browser/site_per_process_hit_test_browsertest.cc

@@ -3571,6 +3571,7 @@ class SitePerProcessGestureHitTestBrowserTest
         ui::ET_GESTURE_SCROLL_BEGIN);
     gesture_scroll_begin_details.set_device_type(
         ui::GestureDeviceType::DEVICE_TOUCHSCREEN);
+    gesture_scroll_begin_details.set_touch_points(2);
     ui::GestureEvent gesture_scroll_begin(
         position.x(), position.y(), 0, ui::EventTimeForNow(),
         gesture_scroll_begin_details, touch_pressed.unique_event_id());