Use scroll-boundary-behavior to control overscroll-refresh/glow on android.

ui/android/overscroll_refresh.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 "ui/android/overscroll_refresh.h"
 
 #include "base/logging.h"
 #include "ui/android/overscroll_refresh_handler.h"
 
 namespace ui {
 namespace {
 
 // Experimentally determined constant used to allow activation even if touch
 // release results in a small upward fling (quite common during a slow scroll).
 const float kMinFlingVelocityForActivation = -500.f;
 
 }  // namespace
 
 OverscrollRefresh::OverscrollRefresh(OverscrollRefreshHandler* handler)
     : scrolled_to_top_(true),
       overflow_y_hidden_(false),
       scroll_consumption_state_(DISABLED),
-      handler_(handler) {
-  DCHECK(handler);
-}
+      handler_(handler) {}
 
 OverscrollRefresh::~OverscrollRefresh() {
 }
 
 void OverscrollRefresh::Reset() {
   scroll_consumption_state_ = DISABLED;
+  DCHECK(handler_);
   handler_->PullReset();
 }
 
 void OverscrollRefresh::OnScrollBegin() {
   ReleaseWithoutActivation();
   if (scrolled_to_top_ && !overflow_y_hidden_)
     scroll_consumption_state_ = AWAITING_SCROLL_UPDATE_ACK;
 }
 
 void OverscrollRefresh::OnScrollEnd(const gfx::Vector2dF& scroll_velocity) {
   bool allow_activation = scroll_velocity.y() > kMinFlingVelocityForActivation;
   Release(allow_activation);
 }
 
-void OverscrollRefresh::OnScrollUpdateAck(bool was_consumed) {
+void OverscrollRefresh::OnOverscrolled(bool can_navigate) {
   if (scroll_consumption_state_ != AWAITING_SCROLL_UPDATE_ACK)
     return;
 
-  if (was_consumed) {
+  if (!can_navigate) {
     scroll_consumption_state_ = DISABLED;
     return;
   }
 
+  DCHECK(handler_);
   scroll_consumption_state_ = handler_->PullStart() ? ENABLED : DISABLED;
 }
 
 bool OverscrollRefresh::WillHandleScrollUpdate(
     const gfx::Vector2dF& scroll_delta) {
   switch (scroll_consumption_state_) {
     case DISABLED:
       return false;
 
     case AWAITING_SCROLL_UPDATE_ACK:
       // If the initial scroll motion is downward, never allow activation.
       if (scroll_delta.y() <= 0)
         scroll_consumption_state_ = DISABLED;
       return false;
 
     case ENABLED:
+      DCHECK(handler_);
       handler_->PullUpdate(scroll_delta.y());
       return true;
   }
 
   NOTREACHED() << "Invalid overscroll state: " << scroll_consumption_state_;
   return false;
 }
 
 void OverscrollRefresh::ReleaseWithoutActivation() {
   bool allow_activation = false;
   Release(allow_activation);
 }
 
 bool OverscrollRefresh::IsActive() const {
   return scroll_consumption_state_ == ENABLED;
 }
 
 bool OverscrollRefresh::IsAwaitingScrollUpdateAck() const {
   return scroll_consumption_state_ == AWAITING_SCROLL_UPDATE_ACK;
 }
 
 void OverscrollRefresh::OnFrameUpdated(
     const gfx::Vector2dF& content_scroll_offset,
     bool root_overflow_y_hidden) {
   scrolled_to_top_ = content_scroll_offset.y() == 0;
   overflow_y_hidden_ = root_overflow_y_hidden;
 }
 
 void OverscrollRefresh::Release(bool allow_refresh) {
-  if (scroll_consumption_state_ == ENABLED)
+  if (scroll_consumption_state_ == ENABLED) {
+    DCHECK(handler_);
     handler_->PullRelease(allow_refresh);
+  }
   scroll_consumption_state_ = DISABLED;
 }
 
 }  // namespace ui