Add support for touch-action: pinch-zoom.

content/browser/renderer_host/input/touch_action_filter.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/input/touch_action_filter.h"
 
 #include <math.h>
 
 #include "base/logging.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
@@ skipping 70 matching lines @@
           gesture_event->type = WebInputEvent::GestureScrollEnd;
         }
       }
       return FilterScrollEndingGesture();
 
     case WebInputEvent::GestureScrollEnd:
       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

[Rick Byers, 2016/07/07 21:09:14]

Ah crap, I forgot about this comment I left.

I think this change may break some things.  IIRC we may depend on
GesturePinchUpdate occuring inside of a GestureScroll sequence (pinch events
outside of a scroll sequence were impossible before AFAIK).

Also if we're actually inside of a pinch sequence, then we probably want to
allow scroll events so that two-finger panning during a pinch still works in a
'touch-action: pinch-zoom' region.  Let's chat about options here.

-        // 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;
-      }
+      drop_pinch_gesture_events_ =
+          (allowed_touch_action_ & TOUCH_ACTION_PINCH_ZOOM) != 0;
       return drop_pinch_gesture_events_;
 
     case WebInputEvent::GesturePinchUpdate:
       return drop_pinch_gesture_events_;
 
     case WebInputEvent::GesturePinchEnd:
       if (drop_pinch_gesture_events_) {
         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
     // filtered out, replace it with a tap event.
     case WebInputEvent::GestureDoubleTap:
       DCHECK_EQ(1, gesture_event->data.tap.tapCount);
       if (!allow_current_double_tap_event_)
         gesture_event->type = WebInputEvent::GestureTap;
       allow_current_double_tap_event_ = true;
       break;
@@ skipping 98 matching lines @@
     } else if (gesture_event.data.scrollBegin.deltaYHint < 0 &&
                allowed_touch_action_ & TOUCH_ACTION_PAN_DOWN) {
       return false;
     } else {
       return true;
     }
   }
 }
 
 }  // namespace content