Revert of Cleanup viewport scrolling for future scroll customization work.

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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 "cc/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <set>
@@ skipping 2592 matching lines @@
       layer_impl->CurrentScrollOffset() - previous_offset;
   gfx::Vector2dF consumed_scroll(scrolled.x(), scrolled.y());
   consumed_scroll.Scale(page_scale_factor);
 
   return consumed_scroll;
 }
 
 gfx::Vector2dF LayerTreeHostImpl::ScrollLayer(LayerImpl* layer_impl,
                                               const gfx::Vector2dF& delta,
                                               const gfx::Point& viewport_point,
-                                              bool is_direct_manipulation) {
-  // Events representing direct manipulation of the screen (such as gesture
-  // events) need to be transformed from viewport coordinates to local layer
-  // coordinates so that the scrolling contents exactly follow the user's
-  // finger. In contrast, events not representing direct manipulation of the
-  // screen (such as wheel events) represent a fixed amount of scrolling so we
-  // can just apply them directly, but the page scale factor is applied to the
-  // scroll delta.
-  if (is_direct_manipulation)
-    return ScrollLayerWithViewportSpaceDelta(layer_impl, viewport_point, delta);
-  float scale_factor = active_tree()->current_page_scale_factor();
-  return ScrollLayerWithLocalDelta(layer_impl, delta, scale_factor);
+                                              bool is_wheel_scroll) {
+  // Gesture events need to be transformed from viewport coordinates to
+  // local layer coordinates so that the scrolling contents exactly follow
+  // the user's finger. In contrast, wheel events represent a fixed amount
+  // of scrolling so we can just apply them directly, but the page scale
+  // factor is applied to the scroll delta.
+  if (is_wheel_scroll) {
+    float scale_factor = active_tree()->current_page_scale_factor();
+    return ScrollLayerWithLocalDelta(layer_impl,
+                                     delta,
+                                     scale_factor);
+  }
+
+  return ScrollLayerWithViewportSpaceDelta(layer_impl,
+                                           viewport_point,
+                                           delta);
 }
 
 static LayerImpl* nextLayerInScrollOrder(LayerImpl* layer) {
   if (layer->scroll_parent())
     return layer->scroll_parent();
 
   return layer->parent();
 }
 
 InputHandlerScrollResult LayerTreeHostImpl::ScrollBy(
     const gfx::Point& viewport_point,
     const gfx::Vector2dF& scroll_delta) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::ScrollBy");
   if (!CurrentlyScrollingLayer())
     return InputHandlerScrollResult();
 
   gfx::Vector2dF pending_delta = scroll_delta;
   gfx::Vector2dF unused_root_delta;
   bool did_scroll_x = false;
   bool did_scroll_y = false;
+  bool did_scroll_top_controls = false;
 
   if (pinch_gesture_active_ && settings().invert_viewport_scroll_order) {
     // Scrolls during a pinch gesture should pan the visual viewport, rather
     // than a typical bubbling scroll.
     viewport()->Pan(pending_delta);
     return InputHandlerScrollResult();
   }
 
   for (LayerImpl* layer_impl = CurrentlyScrollingLayer();
        layer_impl;
        layer_impl = nextLayerInScrollOrder(layer_impl)) {
     // Skip the outer viewport scroll layer so that we try to scroll the
     // viewport only once. i.e. The inner viewport layer represents the
     // viewport.
     if (!layer_impl->scrollable() || layer_impl == OuterViewportScrollLayer())
       continue;
 
     gfx::Vector2dF applied_delta;
     if (layer_impl == InnerViewportScrollLayer()) {
       bool affect_top_controls = true;
-      applied_delta =
-          viewport()->ScrollBy(pending_delta, viewport_point, !wheel_scrolling_,
-                               affect_top_controls);
-      unused_root_delta = pending_delta - applied_delta;
+      Viewport::ScrollResult result = viewport()->ScrollBy(pending_delta,
+                                                           viewport_point,
+                                                           wheel_scrolling_,
+                                                           affect_top_controls);
+      applied_delta = result.applied_delta;
+      unused_root_delta = result.unused_scroll_delta;
+      did_scroll_top_controls = result.top_controls_applied_delta.y() != 0;
     } else {
-      applied_delta = ScrollLayer(layer_impl, pending_delta, viewport_point,
-                                  !wheel_scrolling_);
+      applied_delta = ScrollLayer(layer_impl,
+                                  pending_delta,
+                                  viewport_point,
+                                  wheel_scrolling_);
     }
 
     // If the layer wasn't able to move, try the next one in the hierarchy.
     const float kEpsilon = 0.1f;
-    bool did_layer_consume_delta_x = std::abs(applied_delta.x()) > kEpsilon;
-    bool did_layer_consume_delta_y = std::abs(applied_delta.y()) > kEpsilon;
+    bool did_move_layer_x = std::abs(applied_delta.x()) > kEpsilon;
+    bool did_move_layer_y = std::abs(applied_delta.y()) > kEpsilon;
+    did_scroll_x |= did_move_layer_x;
+    did_scroll_y |= did_move_layer_y;
 
-    did_scroll_x |= did_layer_consume_delta_x;
-    did_scroll_y |= did_layer_consume_delta_y;
-
-    if (did_layer_consume_delta_x || did_layer_consume_delta_y) {
+    if (did_move_layer_x || did_move_layer_y) {
       did_lock_scrolling_layer_ = true;
 
       // When scrolls are allowed to bubble, it's important that the original
       // scrolling layer be preserved. This ensures that, after a scroll
       // bubbles, the user can reverse scroll directions and immediately resume
       // scrolling the original layer that scrolled.
       if (!should_bubble_scrolls_) {
         active_tree_->SetCurrentlyScrollingLayer(layer_impl);
         break;
       }
@@ skipping 33 matching lines @@
   }
 
   // Scrolling along an axis resets accumulated root overscroll for that axis.
   if (did_scroll_x)
     accumulated_root_overscroll_.set_x(0);
   if (did_scroll_y)
     accumulated_root_overscroll_.set_y(0);
   accumulated_root_overscroll_ += unused_root_delta;
 
   InputHandlerScrollResult scroll_result;
-  scroll_result.did_scroll = did_scroll_content;
+  scroll_result.did_scroll = did_scroll_content || did_scroll_top_controls;
   scroll_result.did_overscroll_root = !unused_root_delta.IsZero();
   scroll_result.accumulated_root_overscroll = accumulated_root_overscroll_;
   scroll_result.unused_scroll_delta = unused_root_delta;
   return scroll_result;
 }
 
 // This implements scrolling by page as described here:
 // http://msdn.microsoft.com/en-us/library/windows/desktop/ms645601(v=vs.85).aspx#_win32_The_Mouse_Wheel
 // for events with WHEEL_PAGESCROLL set.
 bool LayerTreeHostImpl::ScrollVerticallyByPage(const gfx::Point& viewport_point,
@@ skipping 679 matching lines @@
   new_target.SetToMin(layer_impl->MaxScrollOffset());
 
   curve->UpdateTarget(
       animation->TrimTimeToCurrentIteration(CurrentBeginFrameArgs().frame_time)
           .InSecondsF(),
       new_target);
 
   return true;
 }
 }  // namespace cc