[Athena] Fix switching activities by swiping from the right bezel

athena/wm/bezel_controller.cc

 // Copyright 2014 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 "athena/wm/bezel_controller.h"
 
 #include "ui/aura/window.h"
 #include "ui/events/event_handler.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/geometry/point_conversions.h"
@@ skipping 50 matching lines @@
   DCHECK_NE(state, BEZEL_SCROLLING_TWO_FINGERS);
   DCHECK_NE(state, BEZEL_SCROLLING_ONE_FINGER);
   SetState(state, kScrollDeltaNone);
 }
 
 void BezelController::SetState(BezelController::State state,
                                float scroll_delta) {
   if (!left_right_delegate_ || state == state_)
     return;
 
-  if (state == BEZEL_SCROLLING_TWO_FINGERS)
-    left_right_delegate_->ScrollBegin(scroll_bezel_, scroll_delta);
-  else if (state_ == BEZEL_SCROLLING_TWO_FINGERS)
-    left_right_delegate_->ScrollEnd();
+  State old_state = state_;
   state_ = state;
+
   if (state == NONE) {
     scroll_bezel_ = BEZEL_NONE;
     scroll_target_ = NULL;
   }
+
+  if (state == BEZEL_SCROLLING_TWO_FINGERS) {
+    left_right_delegate_->ScrollBegin(scroll_bezel_, scroll_delta);
+  } else if (old_state == BEZEL_SCROLLING_TWO_FINGERS) {
+    // If ScrollEnd() hides |scroll_target_|, ET_GESTURE_END is dispatched
+    // and we get a reentrant call to SetState().
+    left_right_delegate_->ScrollEnd();
+  }
 }
 
 // Only implemented for LEFT and RIGHT bezels ATM.
 BezelController::Bezel BezelController::GetBezel(const gfx::PointF& location) {
   int screen_width = GetDisplay(container_).bounds().width();
   if (location.x() < kBezelWidth) {
     return BEZEL_LEFT;
   } else if (location.x() > screen_width - kBezelWidth) {
     return BEZEL_RIGHT;
   } else {
@@ skipping 90 matching lines @@
     if (state_ != BEZEL_SCROLLING_TWO_FINGERS)
       return;
 
     left_right_delegate_->ScrollUpdate(scroll_delta);
     if (left_right_delegate_->CanScroll())
       event->SetHandled();
   }
 }
 
 }  // namespace athena