Allow changing top controls height

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 <limits>
 #include <set>
 
 #include "base/debug/trace_event.h"
@@ skipping 78 matching lines @@
       min_page_scale_factor_(0),
       max_page_scale_factor_(0),
       scrolling_layer_id_from_previous_tree_(0),
       contents_textures_purged_(false),
       viewport_size_invalid_(false),
       needs_update_draw_properties_(true),
       needs_full_tree_sync_(true),
       next_activation_forces_redraw_(false),
       has_ever_been_drawn_(false),
       render_surface_layer_list_id_(0),
-      top_controls_layout_height_(0),
+      top_controls_shrink_blink_size_(false),
+      top_controls_height_(0),
       top_controls_content_offset_(0),
       top_controls_delta_(0),
       sent_top_controls_delta_(0) {
 }
 
 LayerTreeImpl::~LayerTreeImpl() {
   BreakSwapPromises(SwapPromise::SWAP_FAILS);
 
   // Need to explicitly clear the tree prior to destroying this so that
   // the LayerTreeImpl pointer is still valid in the LayerImpl dtor.
@@ skipping 92 matching lines @@
   // The request queue should have been processed and does not require a push.
   DCHECK_EQ(ui_resource_request_queue_.size(), 0u);
 
   if (next_activation_forces_redraw_) {
     target_tree->ForceRedrawNextActivation();
     next_activation_forces_redraw_ = false;
   }
 
   target_tree->PassSwapPromises(&swap_promise_list_);
 
-  target_tree->top_controls_layout_height_ = top_controls_layout_height_;
+  // Track the change in top controls height to offset the top_controls_delta
+  // properly.  This is so that the top controls offset will be maintained
+  // across height changes.
+  float top_controls_height_delta =
+      target_tree->top_controls_height_ - top_controls_height_;
+
+  target_tree->top_controls_shrink_blink_size_ =
+      top_controls_shrink_blink_size_;
+  target_tree->top_controls_height_ = top_controls_height_;
   target_tree->top_controls_content_offset_ = top_controls_content_offset_;
-  target_tree->top_controls_delta_ =
-      target_tree->top_controls_delta_ -
-          target_tree->sent_top_controls_delta_;
+  target_tree->top_controls_delta_ = target_tree->top_controls_delta_ -
+                                     target_tree->sent_top_controls_delta_ -
+                                     top_controls_height_delta;
   target_tree->sent_top_controls_delta_ = 0.f;
 
   target_tree->SetPageScaleValues(
       page_scale_factor(), min_page_scale_factor(), max_page_scale_factor(),
       target_tree->page_scale_delta() / target_tree->sent_page_scale_delta());
   target_tree->set_sent_page_scale_delta(1);
 
   target_tree->pending_page_scale_animation_ =
       pending_page_scale_animation_.Pass();
 
@@ skipping 1261 matching lines @@
     scoped_ptr<PendingPageScaleAnimation> pending_animation) {
   pending_page_scale_animation_ = pending_animation.Pass();
 }
 
 scoped_ptr<PendingPageScaleAnimation>
     LayerTreeImpl::TakePendingPageScaleAnimation() {
   return pending_page_scale_animation_.Pass();
 }
 
 }  // namespace cc