Notify OverscrollController of gesture events in plugins.

chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.mm

 // 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.
 
 #import "chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.h"
 
 #import "base/mac/sdk_forward_declarations.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_commands.h"
 #include "chrome/browser/ui/browser_finder.h"
@@ skipping 113 matching lines @@
 
 - (void)rendererHandledGestureScrollEvent:(const blink::WebGestureEvent&)event
                                  consumed:(BOOL)consumed {
   switch (event.GetType()) {
     case blink::WebInputEvent::kGestureScrollBegin:
       if (event.data.scroll_begin.synthetic ||
           event.data.scroll_begin.inertial_phase ==
               blink::WebGestureEvent::kMomentumPhase) {
         return;
       }
+      // GestureScrollBegin and GestureScrollEnd events are created to wrap
+      // individual resent GestureScrollUpdates from a plugin. Hence these
+      // should not be used to indicate the beginning/end of the swipe gesture.
+      // TODO(mcnee): When we remove BrowserPlugin, delete this code.
+      // See crbug.com/533069
+      if (event.resending_plugin_id != -1) {

[erikchen, 2017/05/05 19:15:36]

this class is a state machine, and I'm a little bit worried about it ending in
an inconsistent state if there's another layer on top of it consuming and/or
generating events. Can you confirm that we correctly propagate state for the
gesture and touch APIs, e.g. beginGestureWithEvent: and touchesBeganWithEvent:

[Kevin McNee, 2017/05/16 16:24:23]

With a guest, the sequence of calls to touches*WithEvent and *GestureWithEvent
is the same as with a normal page. Looking at a stack trace, these events are
not coming up from the guest.

+        return;
+      }
       waitingForFirstGestureScroll_ = YES;
       break;
     case blink::WebInputEvent::kGestureScrollUpdate:
       if (waitingForFirstGestureScroll_)
         firstScrollUnconsumed_ = !consumed;
       waitingForFirstGestureScroll_ = NO;
       break;
     default:
       break;
   }
@@ skipping 440 matching lines @@
   }
 }
 
 @end
 
 @implementation HistorySwiper (PrivateExposedForTesting)
 + (void)resetMagicMouseState {
   forceMagicMouse = NO;
 }
 @end