Introduce bottom controls to CC and let it respond to scrolling

cc/trees/layer_tree_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_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 67 matching lines @@
       layers_(new OwnedLayerImplList),
       viewport_size_invalid_(false),
       needs_update_draw_properties_(true),
       needs_full_tree_sync_(true),
       next_activation_forces_redraw_(false),
       has_ever_been_drawn_(false),
       have_scroll_event_handlers_(false),
       event_listener_properties_(),
       top_controls_shrink_blink_size_(false),
       top_controls_height_(0),
+      bottom_controls_height_(0),
       top_controls_shown_ratio_(top_controls_shown_ratio) {
   property_trees()->is_main_thread = false;
 }
 
 LayerTreeImpl::~LayerTreeImpl() {
   BreakSwapPromises(IsActiveTree() ? SwapPromise::SWAP_FAILS
                                    : SwapPromise::ACTIVATION_FAILS);
 
   // Need to explicitly clear the tree prior to destroying this so that
   // the LayerTreeImpl pointer is still valid in the LayerImpl dtor.
@@ skipping 325 matching lines @@
   if (next_activation_forces_redraw_) {
     target_tree->ForceRedrawNextActivation();
     next_activation_forces_redraw_ = false;
   }
 
   target_tree->PassSwapPromises(std::move(swap_promise_list_));
 
   target_tree->set_top_controls_shrink_blink_size(
       top_controls_shrink_blink_size_);
   target_tree->set_top_controls_height(top_controls_height_);
+  target_tree->set_bottom_controls_height(bottom_controls_height_);
   target_tree->PushTopControls(nullptr);
 
   // Active tree already shares the page_scale_factor object with pending
   // tree so only the limits need to be provided.
   target_tree->PushPageScaleFactorAndLimits(nullptr, min_page_scale_factor(),
                                             max_page_scale_factor());
   target_tree->SetDeviceScaleFactor(device_scale_factor());
   target_tree->set_painted_device_scale_factor(painted_device_scale_factor());
   target_tree->elastic_overscroll()->PushPendingToActive();
 
@@ skipping 320 matching lines @@
 
 void LayerTreeImpl::set_top_controls_height(float top_controls_height) {
   if (top_controls_height_ == top_controls_height)
     return;
 
   top_controls_height_ = top_controls_height;
   if (IsActiveTree())
     layer_tree_host_impl_->UpdateViewportContainerSizes();
 }
 
+void LayerTreeImpl::set_bottom_controls_height(float bottom_controls_height) {
+  if (bottom_controls_height_ == bottom_controls_height)
+    return;
+
+  bottom_controls_height_ = bottom_controls_height;
+  if (IsActiveTree())
+    layer_tree_host_impl_->UpdateViewportContainerSizes();
+}
+
 bool LayerTreeImpl::ClampTopControlsShownRatio() {
   float ratio = top_controls_shown_ratio_->Current(true);
   ratio = std::max(ratio, 0.f);
   ratio = std::min(ratio, 1.f);
   return top_controls_shown_ratio_->SetCurrent(ratio);
 }
 
 bool LayerTreeImpl::SetCurrentTopControlsShownRatio(float ratio) {
   bool changed = top_controls_shown_ratio_->SetCurrent(ratio);
   changed |= ClampTopControlsShownRatio();
@@ skipping 1258 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks and replicas.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc