Add support for touch-action: pinch-zoom.

content/browser/renderer_host/input/touch_action_filter.cc

Index: content/browser/renderer_host/input/touch_action_filter.cc
diff --git a/content/browser/renderer_host/input/touch_action_filter.cc b/content/browser/renderer_host/input/touch_action_filter.cc
index e8f23354bd6a27e205fc3d3cad77030a70268ff8..19c1ce700670e86a4e34d2a664fea14079090121 100644
--- a/content/browser/renderer_host/input/touch_action_filter.cc
+++ b/content/browser/renderer_host/input/touch_action_filter.cc
@@ -44,6 +44,9 @@ bool TouchActionFilter::FilterGestureEvent(WebGestureEvent* gesture_event) {
   switch (gesture_event->type) {
     case WebInputEvent::GestureScrollBegin:
       DCHECK(!drop_scroll_gesture_events_);
+      DCHECK(!drop_pinch_gesture_events_);
+      drop_pinch_gesture_events_ =
+          (allowed_touch_action_ & TOUCH_ACTION_PINCH_ZOOM) == 0;
       drop_scroll_gesture_events_ = ShouldSuppressScroll(*gesture_event);
       return drop_scroll_gesture_events_;
 
@@ -87,17 +90,6 @@ bool TouchActionFilter::FilterGestureEvent(WebGestureEvent* gesture_event) {
       return FilterScrollEndingGesture();
 
     case WebInputEvent::GesturePinchBegin:
-      DCHECK(!drop_pinch_gesture_events_);
-      if (allowed_touch_action_ & TOUCH_ACTION_PINCH_ZOOM) {
-        // Pinch events are always bracketed by scroll events, and the W3C
-        // standard touch-action provides no way to disable scrolling without
-        // also disabling pinching (validated by the IPC ENUM traits).
-        DCHECK(allowed_touch_action_ == TOUCH_ACTION_AUTO ||
-            allowed_touch_action_ == TOUCH_ACTION_MANIPULATION);
-        DCHECK(!drop_scroll_gesture_events_);
-      } else {
-        drop_pinch_gesture_events_ = true;
-      }
       return drop_pinch_gesture_events_;
 
     case WebInputEvent::GesturePinchUpdate:
@@ -108,7 +100,6 @@ bool TouchActionFilter::FilterGestureEvent(WebGestureEvent* gesture_event) {
         drop_pinch_gesture_events_ = false;
         return true;
       }
-      DCHECK(!drop_scroll_gesture_events_);
       break;
 
     // The double tap gesture is a tap ending event. If a double tap gesture is
@@ -156,7 +147,7 @@ bool TouchActionFilter::FilterGestureEvent(WebGestureEvent* gesture_event) {
 }
 
 bool TouchActionFilter::FilterScrollEndingGesture() {
-  DCHECK(!drop_pinch_gesture_events_);
+  drop_pinch_gesture_events_ = false;
   if (drop_scroll_gesture_events_) {
     drop_scroll_gesture_events_ = false;
     return true;
@@ -188,9 +179,18 @@ void TouchActionFilter::ResetTouchAction() {
 bool TouchActionFilter::ShouldSuppressScroll(
     const blink::WebGestureEvent& gesture_event) {
   DCHECK_EQ(gesture_event.type, WebInputEvent::GestureScrollBegin);
+  // if there are two or more pointers then ensure that we allow panning
+  // if pinch-zoom is allowed. Determine if this should really occur in the
+  // GestureScrollBegin or not; see crbug.com/649034.
+  if (!drop_pinch_gesture_events_ &&
+       gesture_event.data.scrollBegin.pointerCount >= 2) {
+    return false;
+  }
+
   if ((allowed_touch_action_ & TOUCH_ACTION_PAN) == TOUCH_ACTION_PAN)
     // All possible panning is enabled.
     return false;
+
   if (!(allowed_touch_action_ & TOUCH_ACTION_PAN))
     // No panning is enabled.
     return true;