11 files changed, 342 insertions, 384 deletions

diff --git a/cc/input/top_controls_manager.cc b/cc/input/top_controls_manager.cc
index 1615d7f..615afb0 100644
--- a/cc/input/top_controls_manager.cc
+++ b/cc/input/top_controls_manager.cc
@@ -39,7 +39,6 @@ TopControlsManager::TopControlsManager(TopControlsManagerClient* client,
     : client_(client),
       animation_direction_(NO_ANIMATION),
       permitted_state_(BOTH),
-      top_controls_height_(0.f),
       current_scroll_delta_(0.f),
       controls_scroll_begin_offset_(0.f),
       top_controls_show_threshold_(top_controls_hide_threshold),
@@ -51,12 +50,20 @@ TopControlsManager::TopControlsManager(TopControlsManagerClient* client,
 TopControlsManager::~TopControlsManager() {
 }
 
-float TopControlsManager::ControlsTopOffset() {
-  return client_->ControlsTopOffset();
+float TopControlsManager::ControlsTopOffset() const {
+  return ContentTopOffset() - TopControlsHeight();
 }
 
-float TopControlsManager::ContentTopOffset() {
-  return client_->ControlsTopOffset() + top_controls_height_;
+float TopControlsManager::ContentTopOffset() const {
+  return TopControlsShownRatio() * TopControlsHeight();
+}
+
+float TopControlsManager::TopControlsShownRatio() const {
+  return client_->CurrentTopControlsShownRatio();
+}
+
+float TopControlsManager::TopControlsHeight() const {
+  return client_->TopControlsHeight();
 }
 
 void TopControlsManager::UpdateTopControlsState(TopControlsState constraints,
@@ -72,31 +79,25 @@ void TopControlsManager::UpdateTopControlsState(TopControlsState constraints,
     return;
 
   // Don't do anything if there is no change in offset.
-  float final_controls_position = 0.f;
-  if (constraints == HIDDEN || current == HIDDEN) {
-    final_controls_position = -top_controls_height_;
-  }
-  if (final_controls_position == client_->ControlsTopOffset()) {
+  float final_shown_ratio = 1.f;
+  if (constraints == HIDDEN || current == HIDDEN)
+    final_shown_ratio = 0.f;
+  if (final_shown_ratio == TopControlsShownRatio())
     return;
-  }
 
-  AnimationDirection animation_direction = SHOWING_CONTROLS;
-  if (constraints == HIDDEN || current == HIDDEN)
-    animation_direction = HIDING_CONTROLS;
-  ResetAnimations();
   if (animate) {
-    SetupAnimation(animation_direction);
+    SetupAnimation(final_shown_ratio ? SHOWING_CONTROLS : HIDING_CONTROLS);
   } else {
-    client_->SetControlsTopOffset(final_controls_position);
+    ResetAnimations();
+    client_->SetCurrentTopControlsShownRatio(final_shown_ratio);
   }
-  client_->DidChangeTopControlsPosition();
 }
 
 void TopControlsManager::ScrollBegin() {
   DCHECK(!pinch_gesture_active_);
   ResetAnimations();
   current_scroll_delta_ = 0.f;
-  controls_scroll_begin_offset_ = client_->ControlsTopOffset();
+  controls_scroll_begin_offset_ = ContentTopOffset();
 }
 
 gfx::Vector2dF TopControlsManager::ScrollBy(
@@ -111,19 +112,21 @@ gfx::Vector2dF TopControlsManager::ScrollBy(
 
   current_scroll_delta_ += pending_delta.y();
 
-  float old_offset = client_->ControlsTopOffset();
-  SetControlsTopOffset(controls_scroll_begin_offset_ - current_scroll_delta_);
+  float old_offset = ContentTopOffset();
+  client_->SetCurrentTopControlsShownRatio(
+      (controls_scroll_begin_offset_ - current_scroll_delta_) /
+      TopControlsHeight());
 
   // If the controls are fully visible, treat the current position as the
   // new baseline even if the gesture didn't end.
-  if (client_->ControlsTopOffset() == 0.f) {
+  if (TopControlsShownRatio() == 1.f) {
     current_scroll_delta_ = 0.f;
-    controls_scroll_begin_offset_ = 0.f;
+    controls_scroll_begin_offset_ = ContentTopOffset();
   }
 
   ResetAnimations();
 
-  gfx::Vector2dF applied_delta(0.f, old_offset - client_->ControlsTopOffset());
+  gfx::Vector2dF applied_delta(0.f, old_offset - ContentTopOffset());
   return pending_delta - applied_delta;
 }
 
@@ -146,44 +149,20 @@ void TopControlsManager::PinchEnd() {
   ScrollBegin();
 }
 
-void TopControlsManager::SetControlsTopOffset(float controls_top_offset) {
-  controls_top_offset = std::max(controls_top_offset, -top_controls_height_);
-  controls_top_offset = std::min(controls_top_offset, 0.f);
-
-  if (client_->ControlsTopOffset() == controls_top_offset)
-    return;
-
-  client_->SetControlsTopOffset(controls_top_offset);
-
-  client_->DidChangeTopControlsPosition();
-}
-
-void TopControlsManager::SetTopControlsHeight(float top_controls_height) {
-  DCHECK_GE(top_controls_height, 0);
-
-  if (top_controls_height == top_controls_height_)
-    return;
-
-  ResetAnimations();
-  float top_controls_offset = client_->ControlsTopOffset();
-  top_controls_height_ = top_controls_height;
-  SetControlsTopOffset(top_controls_offset);
-  StartAnimationIfNecessary();
-}
-
 gfx::Vector2dF TopControlsManager::Animate(base::TimeTicks monotonic_time) {
   if (!top_controls_animation_ || !client_->HaveRootScrollLayer())
     return gfx::Vector2dF();
 
   base::TimeDelta time = monotonic_time - base::TimeTicks();
 
-  float old_offset = client_->ControlsTopOffset();
-  SetControlsTopOffset(top_controls_animation_->GetValue(time));
+  float old_offset = ContentTopOffset();
+  client_->SetCurrentTopControlsShownRatio(
+      top_controls_animation_->GetValue(time));
 
   if (IsAnimationCompleteAtTime(monotonic_time))
     ResetAnimations();
 
-  gfx::Vector2dF scroll_delta(0.f, client_->ControlsTopOffset() - old_offset);
+  gfx::Vector2dF scroll_delta(0.f, ContentTopOffset() - old_offset);
   return scroll_delta;
 }
 
@@ -193,15 +172,9 @@ void TopControlsManager::ResetAnimations() {
 }
 
 void TopControlsManager::SetupAnimation(AnimationDirection direction) {
-  DCHECK(direction != NO_ANIMATION);
-
-  if (direction == SHOWING_CONTROLS && client_->ControlsTopOffset() == 0)
-    return;
-
-  if (direction == HIDING_CONTROLS &&
-      client_->ControlsTopOffset() == -top_controls_height_) {
-    return;
-  }
+  DCHECK_NE(NO_ANIMATION, direction);
+  DCHECK_IMPLIES(direction == HIDING_CONTROLS, TopControlsShownRatio() > 0.f);
+  DCHECK_IMPLIES(direction == SHOWING_CONTROLS, TopControlsShownRatio() < 1.f);
 
   if (top_controls_animation_ && animation_direction_ == direction)
     return;
@@ -209,42 +182,32 @@ void TopControlsManager::SetupAnimation(AnimationDirection direction) {
   top_controls_animation_ = KeyframedFloatAnimationCurve::Create();
   base::TimeDelta start_time = gfx::FrameTime::Now() - base::TimeTicks();
   top_controls_animation_->AddKeyframe(
-      FloatKeyframe::Create(start_time, client_->ControlsTopOffset(), nullptr));
-  float max_ending_offset =
-      (direction == SHOWING_CONTROLS ? 1 : -1) * top_controls_height_;
+      FloatKeyframe::Create(start_time, TopControlsShownRatio(), nullptr));
+  float max_ending_ratio = (direction == SHOWING_CONTROLS ? 1 : -1);
   top_controls_animation_->AddKeyframe(FloatKeyframe::Create(
       start_time + base::TimeDelta::FromMilliseconds(kShowHideMaxDurationMs),
-      client_->ControlsTopOffset() + max_ending_offset,
+      TopControlsShownRatio() + max_ending_ratio,
       EaseTimingFunction::Create()));
   animation_direction_ = direction;
   client_->DidChangeTopControlsPosition();
 }
 
 void TopControlsManager::StartAnimationIfNecessary() {
-  if (client_->ControlsTopOffset() != 0
-      && client_->ControlsTopOffset() != -top_controls_height_) {
-    AnimationDirection show_controls = NO_ANIMATION;
-
-    float top_controls_show_height =
-        top_controls_height_ * top_controls_hide_threshold_;
-    float top_controls_hide_height =
-        top_controls_height_ * (1.f - top_controls_show_threshold_);
-    if (client_->ControlsTopOffset() >= -top_controls_show_height) {
-      // If we're showing so much that the hide threshold won't trigger, show.
-      show_controls = SHOWING_CONTROLS;
-    } else if (client_->ControlsTopOffset() <= -top_controls_hide_height) {
-      // If we're showing so little that the show threshold won't trigger, hide.
-      show_controls = HIDING_CONTROLS;
-    } else {
-      // If we could be either showing or hiding, we determine which one to
-      // do based on whether or not the total scroll delta was moving up or
-      // down.
-      show_controls = current_scroll_delta_ <= 0.f ?
-          SHOWING_CONTROLS : HIDING_CONTROLS;
-    }
-
-    if (show_controls != NO_ANIMATION)
-      SetupAnimation(show_controls);
+  if (TopControlsShownRatio() == 0.f || TopControlsShownRatio() == 1.f)
+    return;
+
+  if (TopControlsShownRatio() >= 1.f - top_controls_hide_threshold_) {
+    // If we're showing so much that the hide threshold won't trigger, show.
+    SetupAnimation(SHOWING_CONTROLS);
+  } else if (TopControlsShownRatio() <= top_controls_show_threshold_) {
+    // If we're showing so little that the show threshold won't trigger, hide.
+    SetupAnimation(HIDING_CONTROLS);
+  } else {
+    // If we could be either showing or hiding, we determine which one to
+    // do based on whether or not the total scroll delta was moving up or
+    // down.
+    SetupAnimation(current_scroll_delta_ <= 0.f ? SHOWING_CONTROLS
+                                                : HIDING_CONTROLS);
   }
 }
 
@@ -253,11 +216,10 @@ bool TopControlsManager::IsAnimationCompleteAtTime(base::TimeTicks time) {
     return true;
 
   base::TimeDelta animation_time = time - base::TimeTicks();
-  float new_offset = top_controls_animation_->GetValue(animation_time);
+  float new_ratio = top_controls_animation_->GetValue(animation_time);
 
-  if ((animation_direction_ == SHOWING_CONTROLS && new_offset >= 0) ||
-      (animation_direction_ == HIDING_CONTROLS
-          && new_offset <= -top_controls_height_)) {
+  if ((animation_direction_ == SHOWING_CONTROLS && new_ratio >= 1.f) ||
+      (animation_direction_ == HIDING_CONTROLS && new_ratio <= 0.f)) {
     return true;
   }
   return false;
diff --git a/cc/input/top_controls_manager.h b/cc/input/top_controls_manager.h
index 69408ae..06f623d 100644
--- a/cc/input/top_controls_manager.h
+++ b/cc/input/top_controls_manager.h
@@ -38,8 +38,10 @@ class CC_EXPORT TopControlsManager
       float top_controls_hide_threshold);
   virtual ~TopControlsManager();
 
-  float ControlsTopOffset();
-  float ContentTopOffset();
+  float ControlsTopOffset() const;
+  float ContentTopOffset() const;
+  float TopControlsShownRatio() const;
+  float TopControlsHeight() const;
 
   KeyframedFloatAnimationCurve* animation() {
     return top_controls_animation_.get();
@@ -60,9 +62,6 @@ class CC_EXPORT TopControlsManager
   void PinchEnd();
 
   gfx::Vector2dF Animate(base::TimeTicks monotonic_time);
-  void SetControlsTopOffset(float offset);
-  void SetTopControlsHeight(float top_controls_height);
-  float top_controls_height() { return top_controls_height_; }
 
  protected:
   TopControlsManager(TopControlsManagerClient* client,
@@ -81,7 +80,6 @@ class CC_EXPORT TopControlsManager
   scoped_ptr<KeyframedFloatAnimationCurve> top_controls_animation_;
   AnimationDirection animation_direction_;
   TopControlsState permitted_state_;
-  float top_controls_height_;
 
   float current_scroll_delta_;
   float controls_scroll_begin_offset_;
diff --git a/cc/input/top_controls_manager_client.h b/cc/input/top_controls_manager_client.h
index 53b5978..a0f2f5b 100644
--- a/cc/input/top_controls_manager_client.h
+++ b/cc/input/top_controls_manager_client.h
@@ -11,8 +11,9 @@ class LayerTreeImpl;
 
 class CC_EXPORT TopControlsManagerClient {
  public:
-  virtual void SetControlsTopOffset(float offset) = 0;
-  virtual float ControlsTopOffset() const = 0;
+  virtual float TopControlsHeight() const = 0;
+  virtual void SetCurrentTopControlsShownRatio(float ratio) = 0;
+  virtual float CurrentTopControlsShownRatio() const = 0;
   virtual void DidChangeTopControlsPosition() = 0;
   virtual bool HaveRootScrollLayer() const = 0;
 
diff --git a/cc/input/top_controls_manager_unittest.cc b/cc/input/top_controls_manager_unittest.cc
index 0be40ca..f2bff09 100644
--- a/cc/input/top_controls_manager_unittest.cc
+++ b/cc/input/top_controls_manager_unittest.cc
@@ -4,6 +4,8 @@
 
 #include "cc/input/top_controls_manager.h"
 
+#include <algorithm>
+
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "cc/input/top_controls_manager_client.h"
@@ -27,13 +29,13 @@ class MockTopControlsManagerClient : public TopControlsManagerClient {
       : host_impl_(&proxy_, &shared_bitmap_manager_),
         redraw_needed_(false),
         update_draw_properties_needed_(false),
-        top_controls_top_offset_(0.f),
+        top_controls_shown_ratio_(1.f),
         top_controls_height_(top_controls_height),
         top_controls_show_threshold_(top_controls_show_threshold),
         top_controls_hide_threshold_(top_controls_hide_threshold) {
-    active_tree_ =
-        LayerTreeImpl::create(&host_impl_, new SyncedProperty<ScaleGroup>,
-                              new SyncedElasticOverscroll);
+    active_tree_ = LayerTreeImpl::create(
+        &host_impl_, new SyncedProperty<ScaleGroup>, new SyncedTopControls,
+        new SyncedElasticOverscroll);
     root_scroll_layer_ = LayerImpl::Create(active_tree_.get(), 1);
   }
 
@@ -46,11 +48,17 @@ class MockTopControlsManagerClient : public TopControlsManagerClient {
 
   bool HaveRootScrollLayer() const override { return true; }
 
-  void SetControlsTopOffset(float offset) override {
-    top_controls_top_offset_ = offset;
+  float TopControlsHeight() const override { return top_controls_height_; }
+
+  void SetCurrentTopControlsShownRatio(float ratio) override {
+    ratio = std::max(ratio, 0.f);
+    ratio = std::min(ratio, 1.f);
+    top_controls_shown_ratio_ = ratio;
   }
 
-  float ControlsTopOffset() const override { return top_controls_top_offset_; }
+  float CurrentTopControlsShownRatio() const override {
+    return top_controls_shown_ratio_;
+  }
 
   LayerImpl* rootScrollLayer() {
     return root_scroll_layer_.get();
@@ -61,11 +69,12 @@ class MockTopControlsManagerClient : public TopControlsManagerClient {
       manager_ = TopControlsManager::Create(this,
                                             top_controls_show_threshold_,
                                             top_controls_hide_threshold_);
-      manager_->SetTopControlsHeight(top_controls_height_);
     }
     return manager_.get();
   }
 
+  void SetTopControlsHeight(float height) { top_controls_height_ = height; }
+
  private:
   FakeImplProxy proxy_;
   TestSharedBitmapManager shared_bitmap_manager_;
@@ -76,7 +85,7 @@ class MockTopControlsManagerClient : public TopControlsManagerClient {
   bool redraw_needed_;
   bool update_draw_properties_needed_;
 
-  float top_controls_top_offset_;
+  float top_controls_shown_ratio_;
   float top_controls_height_;
   float top_controls_show_threshold_;
   float top_controls_hide_threshold_;
@@ -90,38 +99,38 @@ TEST(TopControlsManagerTest, EnsureScrollThresholdApplied) {
 
   // Scroll down to hide the controls entirely.
   manager->ScrollBy(gfx::Vector2dF(0.f, 30.f));
-  EXPECT_EQ(-30.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-30.f, manager->ControlsTopOffset());
 
   manager->ScrollBy(gfx::Vector2dF(0.f, 30.f));
-  EXPECT_EQ(-60.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-60.f, manager->ControlsTopOffset());
 
   manager->ScrollBy(gfx::Vector2dF(0.f, 100.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
 
   // Scroll back up a bit and ensure the controls don't move until we cross
   // the threshold.
   manager->ScrollBy(gfx::Vector2dF(0.f, -10.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
 
   manager->ScrollBy(gfx::Vector2dF(0.f, -50.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
 
   // After hitting the threshold, further scrolling up should result in the top
   // controls showing.
   manager->ScrollBy(gfx::Vector2dF(0.f, -10.f));
-  EXPECT_EQ(-90.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-90.f, manager->ControlsTopOffset());
 
   manager->ScrollBy(gfx::Vector2dF(0.f, -50.f));
-  EXPECT_EQ(-40.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-40.f, manager->ControlsTopOffset());
 
   // Reset the scroll threshold by going further up the page than the initial
   // threshold.
   manager->ScrollBy(gfx::Vector2dF(0.f, -100.f));
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
 
   // See that scrolling down the page now will result in the controls hiding.
   manager->ScrollBy(gfx::Vector2dF(0.f, 20.f));
-  EXPECT_EQ(-20.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-20.f, manager->ControlsTopOffset());
 
   manager->ScrollEnd();
 }
@@ -131,14 +140,14 @@ TEST(TopControlsManagerTest, PartialShownHideAnimation) {
   TopControlsManager* manager = client.manager();
   manager->ScrollBegin();
   manager->ScrollBy(gfx::Vector2dF(0.f, 300.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
   manager->ScrollEnd();
 
   manager->ScrollBegin();
   manager->ScrollBy(gfx::Vector2dF(0.f, -15.f));
-  EXPECT_EQ(-85.f, manager->ControlsTopOffset());
-  EXPECT_EQ(15.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-85.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(15.f, manager->ContentTopOffset());
   manager->ScrollEnd();
 
   EXPECT_TRUE(manager->animation());
@@ -152,8 +161,8 @@ TEST(TopControlsManagerTest, PartialShownHideAnimation) {
     previous_offset = manager->ControlsTopOffset();
   }
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
 }
 
 TEST(TopControlsManagerTest, PartialShownShowAnimation) {
@@ -161,14 +170,14 @@ TEST(TopControlsManagerTest, PartialShownShowAnimation) {
   TopControlsManager* manager = client.manager();
   manager->ScrollBegin();
   manager->ScrollBy(gfx::Vector2dF(0.f, 300.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
   manager->ScrollEnd();
 
   manager->ScrollBegin();
   manager->ScrollBy(gfx::Vector2dF(0.f, -70.f));
-  EXPECT_EQ(-30.f, manager->ControlsTopOffset());
-  EXPECT_EQ(70.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-30.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(70.f, manager->ContentTopOffset());
   manager->ScrollEnd();
 
   EXPECT_TRUE(manager->animation());
@@ -182,8 +191,8 @@ TEST(TopControlsManagerTest, PartialShownShowAnimation) {
     previous_offset = manager->ControlsTopOffset();
   }
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
-  EXPECT_EQ(100.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(100.f, manager->ContentTopOffset());
 }
 
 TEST(TopControlsManagerTest, PartialHiddenWithAmbiguousThresholdShows) {
@@ -193,8 +202,8 @@ TEST(TopControlsManagerTest, PartialHiddenWithAmbiguousThresholdShows) {
   manager->ScrollBegin();
 
   manager->ScrollBy(gfx::Vector2dF(0.f, 20.f));
-  EXPECT_EQ(-20.f, manager->ControlsTopOffset());
-  EXPECT_EQ(80.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-20.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(80.f, manager->ContentTopOffset());
 
   manager->ScrollEnd();
   EXPECT_TRUE(manager->animation());
@@ -208,8 +217,8 @@ TEST(TopControlsManagerTest, PartialHiddenWithAmbiguousThresholdShows) {
     previous_offset = manager->ControlsTopOffset();
   }
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
-  EXPECT_EQ(100.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(100.f, manager->ContentTopOffset());
 }
 
 TEST(TopControlsManagerTest, PartialHiddenWithAmbiguousThresholdHides) {
@@ -219,8 +228,8 @@ TEST(TopControlsManagerTest, PartialHiddenWithAmbiguousThresholdHides) {
   manager->ScrollBegin();
 
   manager->ScrollBy(gfx::Vector2dF(0.f, 30.f));
-  EXPECT_EQ(-30.f, manager->ControlsTopOffset());
-  EXPECT_EQ(70.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-30.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(70.f, manager->ContentTopOffset());
 
   manager->ScrollEnd();
   EXPECT_TRUE(manager->animation());
@@ -234,8 +243,8 @@ TEST(TopControlsManagerTest, PartialHiddenWithAmbiguousThresholdHides) {
     previous_offset = manager->ControlsTopOffset();
   }
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
 }
 
 TEST(TopControlsManagerTest, PartialShownWithAmbiguousThresholdHides) {
@@ -243,14 +252,14 @@ TEST(TopControlsManagerTest, PartialShownWithAmbiguousThresholdHides) {
   TopControlsManager* manager = client.manager();
 
   manager->ScrollBy(gfx::Vector2dF(0.f, 200.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
 
   manager->ScrollBegin();
 
   manager->ScrollBy(gfx::Vector2dF(0.f, -20.f));
-  EXPECT_EQ(-80.f, manager->ControlsTopOffset());
-  EXPECT_EQ(20.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-80.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(20.f, manager->ContentTopOffset());
 
   manager->ScrollEnd();
   EXPECT_TRUE(manager->animation());
@@ -264,8 +273,8 @@ TEST(TopControlsManagerTest, PartialShownWithAmbiguousThresholdHides) {
     previous_offset = manager->ControlsTopOffset();
   }
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
 }
 
 TEST(TopControlsManagerTest, PartialShownWithAmbiguousThresholdShows) {
@@ -273,14 +282,14 @@ TEST(TopControlsManagerTest, PartialShownWithAmbiguousThresholdShows) {
   TopControlsManager* manager = client.manager();
 
   manager->ScrollBy(gfx::Vector2dF(0.f, 200.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
 
   manager->ScrollBegin();
 
   manager->ScrollBy(gfx::Vector2dF(0.f, -30.f));
-  EXPECT_EQ(-70.f, manager->ControlsTopOffset());
-  EXPECT_EQ(30.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-70.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(30.f, manager->ContentTopOffset());
 
   manager->ScrollEnd();
   EXPECT_TRUE(manager->animation());
@@ -294,8 +303,8 @@ TEST(TopControlsManagerTest, PartialShownWithAmbiguousThresholdShows) {
     previous_offset = manager->ControlsTopOffset();
   }
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
-  EXPECT_EQ(100.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(100.f, manager->ContentTopOffset());
 }
 
 TEST(TopControlsManagerTest, PinchIgnoresScroll) {
@@ -304,24 +313,24 @@ TEST(TopControlsManagerTest, PinchIgnoresScroll) {
 
   // Hide the controls.
   manager->ScrollBegin();
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
 
   manager->ScrollBy(gfx::Vector2dF(0.f, 300.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
 
   manager->PinchBegin();
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
 
   // Scrolls are ignored during pinch.
   manager->ScrollBy(gfx::Vector2dF(0.f, -15.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
   manager->PinchEnd();
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
 
   // Scrolls should no long be ignored.
   manager->ScrollBy(gfx::Vector2dF(0.f, -15.f));
-  EXPECT_EQ(-85.f, manager->ControlsTopOffset());
-  EXPECT_EQ(15.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-85.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(15.f, manager->ContentTopOffset());
   manager->ScrollEnd();
 
   EXPECT_TRUE(manager->animation());
@@ -333,7 +342,7 @@ TEST(TopControlsManagerTest, PinchBeginStartsAnimationIfNecessary) {
 
   manager->ScrollBegin();
   manager->ScrollBy(gfx::Vector2dF(0.f, 300.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
 
   manager->PinchBegin();
   EXPECT_FALSE(manager->animation());
@@ -342,8 +351,8 @@ TEST(TopControlsManagerTest, PinchBeginStartsAnimationIfNecessary) {
   EXPECT_FALSE(manager->animation());
 
   manager->ScrollBy(gfx::Vector2dF(0.f, -15.f));
-  EXPECT_EQ(-85.f, manager->ControlsTopOffset());
-  EXPECT_EQ(15.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-85.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(15.f, manager->ContentTopOffset());
 
   manager->PinchBegin();
   EXPECT_TRUE(manager->animation());
@@ -362,8 +371,8 @@ TEST(TopControlsManagerTest, PinchBeginStartsAnimationIfNecessary) {
   EXPECT_FALSE(manager->animation());
 
   manager->ScrollBy(gfx::Vector2dF(0.f, -55.f));
-  EXPECT_EQ(-45.f, manager->ControlsTopOffset());
-  EXPECT_EQ(55.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-45.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(55.f, manager->ContentTopOffset());
   EXPECT_FALSE(manager->animation());
 
   manager->ScrollEnd();
@@ -378,83 +387,64 @@ TEST(TopControlsManagerTest, PinchBeginStartsAnimationIfNecessary) {
     previous_offset = manager->ControlsTopOffset();
   }
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
 }
 
 TEST(TopControlsManagerTest, HeightChangeMaintainsFullyVisibleControls) {
   MockTopControlsManagerClient client(0.f, 0.5f, 0.5f);
   TopControlsManager* manager = client.manager();
 
-  EXPECT_EQ(0.f, manager->top_controls_height());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
 
-  manager->SetTopControlsHeight(100.f);
+  client.SetTopControlsHeight(100.f);
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(100.f, manager->top_controls_height());
-  EXPECT_EQ(0, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(100.f, manager->TopControlsHeight());
+  EXPECT_FLOAT_EQ(0, manager->ControlsTopOffset());
 
-  manager->SetTopControlsHeight(50.f);
+  client.SetTopControlsHeight(50.f);
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(50.f, manager->top_controls_height());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(50.f, manager->TopControlsHeight());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
 }
 
-TEST(TopControlsManagerTest, ShrinkingHeightKeepsTopControlsHidden) {
-  MockTopControlsManagerClient client(100.f, 0.5f, 0.5f);
+TEST(TopControlsManagerTest, GrowingHeightKeepsTopControlsHidden) {
+  MockTopControlsManagerClient client(0.f, 0.5f, 0.5f);
   TopControlsManager* manager = client.manager();
-
-  manager->ScrollBegin();
-  manager->ScrollBy(gfx::Vector2dF(0.f, 300.f));
-  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
+  manager->UpdateTopControlsState(HIDDEN, HIDDEN, false);
+  EXPECT_EQ(0.f, manager->ControlsTopOffset());
   EXPECT_EQ(0.f, manager->ContentTopOffset());
-  manager->ScrollEnd();
 
-  manager->SetTopControlsHeight(50.f);
+  client.SetTopControlsHeight(50.f);
   EXPECT_FALSE(manager->animation());
   EXPECT_EQ(-50.f, manager->ControlsTopOffset());
   EXPECT_EQ(0.f, manager->ContentTopOffset());
 
-  manager->SetTopControlsHeight(0.f);
+  client.SetTopControlsHeight(100.f);
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_EQ(-100.f, manager->ControlsTopOffset());
   EXPECT_EQ(0.f, manager->ContentTopOffset());
 }
 
-TEST(TopControlsManagerTest, HiddenTopControlsReadjustOnIncreasedHeight) {
-  MockTopControlsManagerClient client(10.f, 0.5f, 0.5f);
+TEST(TopControlsManagerTest, ShrinkingHeightKeepsTopControlsHidden) {
+  MockTopControlsManagerClient client(100.f, 0.5f, 0.5f);
   TopControlsManager* manager = client.manager();
 
   manager->ScrollBegin();
   manager->ScrollBy(gfx::Vector2dF(0.f, 300.f));
-  EXPECT_EQ(-10.f, manager->ControlsTopOffset());
-  EXPECT_EQ(0.f, manager->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-100.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
   manager->ScrollEnd();
 
-  manager->SetTopControlsHeight(15.f);
-  EXPECT_TRUE(manager->animation());
-  base::TimeTicks time = base::TimeTicks::Now();
-  float previous_offset = manager->ControlsTopOffset();
-  while (manager->animation()) {
-    time = base::TimeDelta::FromMicroseconds(100) + time;
-    manager->Animate(time);
-    EXPECT_LT(manager->ControlsTopOffset(), previous_offset);
-    previous_offset = manager->ControlsTopOffset();
-  }
+  client.SetTopControlsHeight(50.f);
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(-15.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(-50.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
 
-  manager->SetTopControlsHeight(35.f);
-  EXPECT_TRUE(manager->animation());
-  time = base::TimeTicks::Now();
-  previous_offset = manager->ControlsTopOffset();
-  while (manager->animation()) {
-    time = base::TimeDelta::FromMicroseconds(100) + time;
-    manager->Animate(time);
-    EXPECT_GT(manager->ControlsTopOffset(), previous_offset);
-    previous_offset = manager->ControlsTopOffset();
-  }
+  client.SetTopControlsHeight(0.f);
   EXPECT_FALSE(manager->animation());
-  EXPECT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ControlsTopOffset());
+  EXPECT_FLOAT_EQ(0.f, manager->ContentTopOffset());
 }
+
 }  // namespace
 }  // namespace cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index fa4dd5d..9bac4a8 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -119,7 +119,7 @@ LayerTreeHost::LayerTreeHost(
       debug_state_(settings.initial_debug_state),
       top_controls_shrink_blink_size_(false),
       top_controls_height_(0.f),
-      top_controls_content_offset_(0.f),
+      top_controls_shown_ratio_(0.f),
       device_scale_factor_(1.f),
       visible_(true),
       page_scale_factor_(1.f),
@@ -335,20 +335,10 @@ void LayerTreeHost::FinishCommitOnImplThread(LayerTreeHostImpl* host_impl) {
 
   sync_tree->PassSwapPromises(&swap_promise_list_);
 
-  // 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 =
-      sync_tree->top_controls_height() - top_controls_height_;
-
   sync_tree->set_top_controls_shrink_blink_size(
       top_controls_shrink_blink_size_);
   sync_tree->set_top_controls_height(top_controls_height_);
-  sync_tree->set_top_controls_content_offset(top_controls_content_offset_);
-  sync_tree->set_top_controls_delta(sync_tree->top_controls_delta() -
-                                    sync_tree->sent_top_controls_delta() -
-                                    top_controls_height_delta);
-  sync_tree->set_sent_top_controls_delta(0.f);
+  sync_tree->PushTopControlsFromMainThread(top_controls_shown_ratio_);
 
   host_impl->SetUseGpuRasterization(UseGpuRasterization());
   host_impl->set_gpu_rasterization_status(GetGpuRasterizationStatus());
@@ -691,11 +681,11 @@ void LayerTreeHost::SetTopControlsHeight(float height) {
   SetNeedsCommit();
 }
 
-void LayerTreeHost::SetTopControlsContentOffset(float offset) {
-  if (top_controls_content_offset_ == offset)
+void LayerTreeHost::SetTopControlsShownRatio(float ratio) {
+  if (top_controls_shown_ratio_ == ratio)
     return;
 
-  top_controls_content_offset_ = offset;
+  top_controls_shown_ratio_ = ratio;
   SetNeedsCommit();
 }
 
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index f41e023..da41e4c 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -212,7 +212,7 @@ class CC_EXPORT LayerTreeHost {
   void SetViewportSize(const gfx::Size& device_viewport_size);
   void SetTopControlsShrinkBlinkSize(bool shrink);
   void SetTopControlsHeight(float height);
-  void SetTopControlsContentOffset(float offset);
+  void SetTopControlsShownRatio(float ratio);
 
   gfx::Size device_viewport_size() const { return device_viewport_size_; }
 
@@ -416,7 +416,7 @@ class CC_EXPORT LayerTreeHost {
   gfx::Size device_viewport_size_;
   bool top_controls_shrink_blink_size_;
   float top_controls_height_;
-  float top_controls_content_offset_;
+  float top_controls_shown_ratio_;
   float device_scale_factor_;
 
   bool visible_;
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 672ffe8..eedd46f 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -235,8 +235,9 @@ LayerTreeHostImpl::LayerTreeHostImpl(
   SetDebugState(settings.initial_debug_state);
 
   // LTHI always has an active tree.
-  active_tree_ = LayerTreeImpl::create(this, new SyncedProperty<ScaleGroup>(),
-                                       new SyncedElasticOverscroll);
+  active_tree_ =
+      LayerTreeImpl::create(this, new SyncedProperty<ScaleGroup>(),
+                            new SyncedTopControls, new SyncedElasticOverscroll);
 
   TRACE_EVENT_OBJECT_CREATED_WITH_ID(
       TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::LayerTreeHostImpl", id_);
@@ -1113,8 +1114,10 @@ void LayerTreeHostImpl::BlockNotifyReadyToActivateForTesting(bool block) {
 void LayerTreeHostImpl::ResetTreesForTesting() {
   if (active_tree_)
     active_tree_->DetachLayerTree();
-  active_tree_ = LayerTreeImpl::create(this, active_tree()->page_scale_factor(),
-                                       active_tree()->elastic_overscroll());
+  active_tree_ =
+      LayerTreeImpl::create(this, active_tree()->page_scale_factor(),
+                            active_tree()->top_controls_shown_ratio(),
+                            active_tree()->elastic_overscroll());
   if (pending_tree_)
     pending_tree_->DetachLayerTree();
   pending_tree_ = nullptr;
@@ -1678,9 +1681,9 @@ void LayerTreeHostImpl::UpdateViewportContainerSizes() {
       active_tree_->top_controls_shrink_blink_size()
           ? active_tree_->top_controls_height()
           : 0.f;
-  inner_container->SetBoundsDelta(
-      gfx::Vector2dF(0, top_controls_layout_height -
-                            active_tree_->total_top_controls_content_offset()));
+  inner_container->SetBoundsDelta(gfx::Vector2dF(
+      0,
+      top_controls_layout_height - top_controls_manager_->ContentTopOffset()));
 
   if (!outer_container || outer_container->BoundsForScrolling().IsEmpty())
     return;
@@ -1768,16 +1771,9 @@ void LayerTreeHostImpl::CreatePendingTree() {
   else
     pending_tree_ =
         LayerTreeImpl::create(this, active_tree()->page_scale_factor(),
+                              active_tree()->top_controls_shown_ratio(),
                               active_tree()->elastic_overscroll());
 
-  // Update the delta from the active tree, which may have
-  // adjusted its delta prior to the pending tree being created.
-  DCHECK_EQ(0.f, pending_tree_->sent_top_controls_delta());
-  pending_tree_->set_top_controls_delta(
-      active_tree_->top_controls_delta() -
-      active_tree_->sent_top_controls_delta());
-  pending_tree_->set_top_controls_height(active_tree_->top_controls_height());
-
   client_->OnCanDrawStateChanged(CanDraw());
   TRACE_EVENT_ASYNC_BEGIN0("cc", "PendingTree:waiting", pending_tree_.get());
 }
@@ -1812,14 +1808,6 @@ void LayerTreeHostImpl::ActivateSyncTree() {
     active_tree_->SetRootLayerScrollOffsetDelegate(
         root_layer_scroll_offset_delegate_);
 
-    if (top_controls_manager_) {
-      top_controls_manager_->SetTopControlsHeight(
-          active_tree_->top_controls_height());
-      top_controls_manager_->SetControlsTopOffset(
-          active_tree_->total_top_controls_content_offset() -
-          active_tree_->top_controls_height());
-    }
-
     UpdateViewportContainerSizes();
   } else {
     active_tree_->ProcessUIResourceRequestQueue();
@@ -2298,15 +2286,17 @@ void LayerTreeHostImpl::DidChangeTopControlsPosition() {
   SetFullRootLayerDamage();
 }
 
-void LayerTreeHostImpl::SetControlsTopOffset(float offset) {
-  float current_top_offset = active_tree_->top_controls_content_offset() -
-                             active_tree_->top_controls_height();
-  active_tree_->set_top_controls_delta(offset - current_top_offset);
+float LayerTreeHostImpl::TopControlsHeight() const {
+  return active_tree_->top_controls_height();
+}
+
+void LayerTreeHostImpl::SetCurrentTopControlsShownRatio(float ratio) {
+  if (active_tree_->SetCurrentTopControlsShownRatio(ratio))
+    DidChangeTopControlsPosition();
 }
 
-float LayerTreeHostImpl::ControlsTopOffset() const {
-  return active_tree_->total_top_controls_content_offset() -
-         active_tree_->top_controls_height();
+float LayerTreeHostImpl::CurrentTopControlsShownRatio() const {
+  return active_tree_->CurrentTopControlsShownRatio();
 }
 
 void LayerTreeHostImpl::BindToClient(InputHandlerClient* client) {
@@ -3059,11 +3049,11 @@ scoped_ptr<ScrollAndScaleSet> LayerTreeHostImpl::ProcessScrollDeltas() {
   CollectScrollDeltas(scroll_info.get(), active_tree_->root_layer());
   scroll_info->page_scale_delta =
       active_tree_->page_scale_factor()->PullDeltaForMainThread();
+  scroll_info->top_controls_delta =
+      active_tree()->top_controls_shown_ratio()->PullDeltaForMainThread();
   scroll_info->elastic_overscroll_delta =
       active_tree_->elastic_overscroll()->PullDeltaForMainThread();
   scroll_info->swap_promises.swap(swap_promises_for_main_thread_scroll_update_);
-  scroll_info->top_controls_delta = active_tree()->top_controls_delta();
-  active_tree_->set_sent_top_controls_delta(scroll_info->top_controls_delta);
 
   return scroll_info.Pass();
 }
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index f4052f1..fcdd81e 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -174,11 +174,14 @@ class CC_EXPORT LayerTreeHostImpl
   ScrollElasticityHelper* CreateScrollElasticityHelper() override;
 
   // TopControlsManagerClient implementation.
-  void SetControlsTopOffset(float offset) override;
-  float ControlsTopOffset() const override;
+  float TopControlsHeight() const override;
+  void SetCurrentTopControlsShownRatio(float offset) override;
+  float CurrentTopControlsShownRatio() const override;
   void DidChangeTopControlsPosition() override;
   bool HaveRootScrollLayer() const override;
 
+  void UpdateViewportContainerSizes();
+
   struct CC_EXPORT FrameData : public RenderPassSink {
     FrameData();
     ~FrameData() override;
@@ -530,7 +533,6 @@ class CC_EXPORT LayerTreeHostImpl
       gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager,
       int id);
 
-  void UpdateViewportContainerSizes();
 
   // Virtual for testing.
   virtual void AnimateLayers(base::TimeTicks monotonic_time);
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index b756ebb..23e90e1 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -2461,10 +2461,7 @@ class LayerTreeHostImplTopControlsTest : public LayerTreeHostImplTest {
         LayerTreeHostImplTest::CreateHostImpl(settings, output_surface.Pass());
     if (init && settings.calculate_top_controls_position) {
       host_impl_->active_tree()->set_top_controls_height(top_controls_height_);
-      host_impl_->active_tree()->set_top_controls_delta(top_controls_height_);
-      host_impl_->top_controls_manager()->SetTopControlsHeight(
-          top_controls_height_);
-      host_impl_->DidChangeTopControlsPosition();
+      host_impl_->active_tree()->SetCurrentTopControlsShownRatio(1.f);
     }
     return init;
   }
@@ -2498,6 +2495,7 @@ class LayerTreeHostImplTopControlsTest : public LayerTreeHostImplTest {
     host_impl_->DidChangeTopControlsPosition();
 
     host_impl_->CreatePendingTree();
+    host_impl_->sync_tree()->set_top_controls_height(top_controls_height_);
     root =
         LayerImpl::Create(host_impl_->sync_tree(), 1);
     root_clip =
@@ -2529,6 +2527,7 @@ class LayerTreeHostImplTopControlsTest : public LayerTreeHostImplTest {
       const gfx::Size& scroll_layer_size) {
     CreateHostImpl(settings_, CreateOutputSurface());
     host_impl_->sync_tree()->set_top_controls_shrink_blink_size(true);
+    host_impl_->sync_tree()->set_top_controls_height(top_controls_height_);
     host_impl_->DidChangeTopControlsPosition();
 
     scoped_ptr<LayerImpl> root =
@@ -2607,8 +2606,8 @@ TEST_F(LayerTreeHostImplTopControlsTest, ScrollTopControlsByFractionalAmount) {
       host_impl_->active_tree()->InnerViewportScrollLayer();
   DCHECK(inner_viewport_scroll_layer);
   host_impl_->ScrollEnd();
-  EXPECT_EQ(top_controls_scroll_delta,
-            inner_viewport_scroll_layer->FixedContainerSizeDelta());
+  EXPECT_FLOAT_EQ(top_controls_scroll_delta.y(),
+                  inner_viewport_scroll_layer->FixedContainerSizeDelta().y());
 }
 
 // In this test, the outer viewport is initially unscrollable. We test that a
@@ -2639,8 +2638,7 @@ TEST_F(LayerTreeHostImplTopControlsTest,
 
   // The entire scroll delta should have been used to hide the top controls.
   // The viewport layers should be resized back to their full sizes.
-  EXPECT_EQ(0.f,
-      host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(0.f, host_impl_->active_tree()->CurrentTopControlsShownRatio());
   EXPECT_EQ(0.f, inner_scroll->CurrentScrollOffset().y());
   EXPECT_EQ(100.f, inner_container->BoundsForScrolling().height());
   EXPECT_EQ(100.f, outer_container->BoundsForScrolling().height());
@@ -2662,8 +2660,7 @@ TEST_F(LayerTreeHostImplTopControlsTest,
   // The entire scroll delta should have been used to show the top controls.
   // The outer viewport should be resized to accomodate and scrolled to the
   // bottom of the document to keep the viewport in place.
-  EXPECT_EQ(50.f,
-      host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(1.f, host_impl_->active_tree()->CurrentTopControlsShownRatio());
   EXPECT_EQ(50.f, outer_container->BoundsForScrolling().height());
   EXPECT_EQ(50.f, inner_container->BoundsForScrolling().height());
   EXPECT_EQ(25.f, outer_scroll->CurrentScrollOffset().y());
@@ -2709,8 +2706,8 @@ TEST_F(LayerTreeHostImplTopControlsTest, FixedContainerDelta) {
   gfx::Vector2dF top_controls_scroll_delta(0.f, 20.f);
   host_impl_->top_controls_manager()->ScrollBegin();
   host_impl_->top_controls_manager()->ScrollBy(top_controls_scroll_delta);
-  EXPECT_EQ(top_controls_height_ - top_controls_scroll_delta.y(),
-            host_impl_->top_controls_manager()->ContentTopOffset());
+  EXPECT_FLOAT_EQ(top_controls_height_ - top_controls_scroll_delta.y(),
+                  host_impl_->top_controls_manager()->ContentTopOffset());
   EXPECT_VECTOR_EQ(top_controls_scroll_delta,
                    outer_viewport_scroll_layer->FixedContainerSizeDelta());
   host_impl_->ScrollEnd();
@@ -2747,8 +2744,7 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsScrollableSublayer) {
   DrawFrame();
 
   // Show top controls
-  EXPECT_EQ(top_controls_height_,
-            host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(1.f, host_impl_->active_tree()->CurrentTopControlsShownRatio());
 
   LayerImpl* outer_viewport_scroll_layer =
       host_impl_->active_tree()->OuterViewportScrollLayer();
@@ -2782,7 +2778,7 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsScrollableSublayer) {
   // Top controls should be hidden
   EXPECT_EQ(scroll_delta.y(),
             top_controls_height_ -
-                host_impl_->active_tree()->total_top_controls_content_offset());
+                host_impl_->top_controls_manager()->ContentTopOffset());
 }
 
 // Ensure setting the top controls position explicitly using the setters on the
@@ -2792,14 +2788,18 @@ TEST_F(LayerTreeHostImplTopControlsTest, PositionTopControlsExplicitly) {
   SetupTopControlsAndScrollLayer();
   DrawFrame();
 
-  host_impl_->active_tree()->set_top_controls_delta(0.f);
-  host_impl_->active_tree()->set_top_controls_content_offset(30.f);
-  EXPECT_EQ(30.f, host_impl_->top_controls_manager()->ContentTopOffset());
-  EXPECT_EQ(-20.f, host_impl_->top_controls_manager()->ControlsTopOffset());
+  host_impl_->active_tree()->SetCurrentTopControlsShownRatio(0.f);
+  host_impl_->active_tree()->top_controls_shown_ratio()->PushFromMainThread(
+      30.f / top_controls_height_);
+  host_impl_->active_tree()->top_controls_shown_ratio()->PushPendingToActive();
+  EXPECT_FLOAT_EQ(30.f, host_impl_->top_controls_manager()->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-20.f,
+                  host_impl_->top_controls_manager()->ControlsTopOffset());
 
-  host_impl_->active_tree()->set_top_controls_delta(-30.f);
-  EXPECT_EQ(0.f, host_impl_->top_controls_manager()->ContentTopOffset());
-  EXPECT_EQ(-50.f, host_impl_->top_controls_manager()->ControlsTopOffset());
+  host_impl_->active_tree()->SetCurrentTopControlsShownRatio(0.f);
+  EXPECT_FLOAT_EQ(0.f, host_impl_->top_controls_manager()->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-50.f,
+                  host_impl_->top_controls_manager()->ControlsTopOffset());
 
   host_impl_->DidChangeTopControlsPosition();
 
@@ -2816,18 +2816,22 @@ TEST_F(LayerTreeHostImplTopControlsTest, ApplyDeltaOnTreeActivation) {
   SetupTopControlsAndScrollLayer();
   DrawFrame();
 
-  host_impl_->sync_tree()->set_top_controls_content_offset(15.f);
-
-  host_impl_->active_tree()->set_top_controls_content_offset(20.f);
-  host_impl_->active_tree()->set_top_controls_delta(-20.f);
-  host_impl_->active_tree()->set_sent_top_controls_delta(-5.f);
+  host_impl_->active_tree()->top_controls_shown_ratio()->PushFromMainThread(
+      20.f / top_controls_height_);
+  host_impl_->active_tree()->top_controls_shown_ratio()->PushPendingToActive();
+  host_impl_->active_tree()->SetCurrentTopControlsShownRatio(
+      15.f / top_controls_height_);
+  host_impl_->active_tree()
+      ->top_controls_shown_ratio()
+      ->PullDeltaForMainThread();
+  host_impl_->active_tree()->SetCurrentTopControlsShownRatio(0.f);
+  host_impl_->sync_tree()->PushTopControlsFromMainThread(15.f /
+                                                         top_controls_height_);
 
   host_impl_->DidChangeTopControlsPosition();
   LayerImpl* root_clip_ptr = host_impl_->active_tree()->root_layer();
   EXPECT_EQ(viewport_size_, root_clip_ptr->bounds());
   EXPECT_EQ(0.f, host_impl_->top_controls_manager()->ContentTopOffset());
-  EXPECT_EQ(0.f,
-      host_impl_->active_tree()->total_top_controls_content_offset());
 
   host_impl_->ActivateSyncTree();
 
@@ -2835,11 +2839,13 @@ TEST_F(LayerTreeHostImplTopControlsTest, ApplyDeltaOnTreeActivation) {
   EXPECT_EQ(0.f, host_impl_->top_controls_manager()->ContentTopOffset());
   EXPECT_EQ(viewport_size_, root_clip_ptr->bounds());
 
-  EXPECT_EQ(0.f, host_impl_->active_tree()->sent_top_controls_delta());
-  EXPECT_EQ(-15.f, host_impl_->active_tree()->top_controls_delta());
-  EXPECT_EQ(15.f, host_impl_->active_tree()->top_controls_content_offset());
-  EXPECT_EQ(0.f,
-      host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_FLOAT_EQ(
+      -15.f, host_impl_->active_tree()->top_controls_shown_ratio()->Delta() *
+                 top_controls_height_);
+  EXPECT_FLOAT_EQ(
+      15.f,
+      host_impl_->active_tree()->top_controls_shown_ratio()->ActiveBase() *
+          top_controls_height_);
 }
 
 // Test that changing the top controls layout height is correctly applied to
@@ -2851,11 +2857,13 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsLayoutHeightChanged) {
   SetupTopControlsAndScrollLayer();
   DrawFrame();
 
-  host_impl_->sync_tree()->set_top_controls_content_offset(50.f);
+  host_impl_->sync_tree()->PushTopControlsFromMainThread(1.f);
   host_impl_->sync_tree()->set_top_controls_shrink_blink_size(true);
 
-  host_impl_->active_tree()->set_top_controls_content_offset(50.f);
-  host_impl_->active_tree()->set_top_controls_delta(-50.f);
+  host_impl_->active_tree()->top_controls_shown_ratio()->PushFromMainThread(
+      1.f);
+  host_impl_->active_tree()->top_controls_shown_ratio()->PushPendingToActive();
+  host_impl_->active_tree()->SetCurrentTopControlsShownRatio(0.f);
 
   host_impl_->DidChangeTopControlsPosition();
   LayerImpl* root_clip_ptr = host_impl_->active_tree()->root_layer();
@@ -2877,9 +2885,11 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsLayoutHeightChanged) {
   EXPECT_EQ(viewport_size_, root_clip_ptr->bounds());
   EXPECT_VECTOR_EQ(gfx::Vector2dF(0.f, 50.f), root_clip_ptr->bounds_delta());
 
-  host_impl_->active_tree()->set_top_controls_delta(0.f);
+  host_impl_->active_tree()->SetCurrentTopControlsShownRatio(1.f);
   host_impl_->DidChangeTopControlsPosition();
 
+  EXPECT_EQ(1.f, host_impl_->top_controls_manager()->TopControlsShownRatio());
+  EXPECT_EQ(50.f, host_impl_->top_controls_manager()->TopControlsHeight());
   EXPECT_EQ(50.f, host_impl_->top_controls_manager()->ContentTopOffset());
   EXPECT_VECTOR_EQ(gfx::Vector2dF(0.f, 0.f), root_clip_ptr->bounds_delta());
   EXPECT_EQ(gfx::Size(viewport_size_.width(), viewport_size_.height() - 50.f),
@@ -2894,8 +2904,7 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsViewportOffsetClamping) {
       gfx::Size(100, 100), gfx::Size(200, 200), gfx::Size(200, 400));
   DrawFrame();
 
-  EXPECT_EQ(top_controls_height_,
-            host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(1.f, host_impl_->active_tree()->CurrentTopControlsShownRatio());
 
   LayerImpl* outer_scroll = host_impl_->OuterViewportScrollLayer();
   LayerImpl* inner_scroll = host_impl_->InnerViewportScrollLayer();
@@ -2915,17 +2924,15 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsViewportOffsetClamping) {
   host_impl_->ScrollBy(gfx::Point(), scroll_delta);
 
   // scrolling down at the max extents no longer hides the top controls
-  EXPECT_EQ(0.f,
-            top_controls_height_ -
-                host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(1.f, host_impl_->active_tree()->CurrentTopControlsShownRatio());
 
   // forcefully hide the top controls by 25px
   host_impl_->top_controls_manager()->ScrollBy(scroll_delta);
   host_impl_->ScrollEnd();
 
-  EXPECT_EQ(scroll_delta.y(),
-            top_controls_height_ -
-                host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_FLOAT_EQ(scroll_delta.y(),
+                  top_controls_height_ -
+                      host_impl_->top_controls_manager()->ContentTopOffset());
 
   inner_scroll->ClampScrollToMaxScrollOffset();
   outer_scroll->ClampScrollToMaxScrollOffset();
@@ -2961,8 +2968,8 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsAspectRatio) {
       gfx::Size(100, 100), gfx::Size(200, 200), gfx::Size(200, 400));
   DrawFrame();
 
-  EXPECT_EQ(top_controls_height_,
-            host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_FLOAT_EQ(top_controls_height_,
+                  host_impl_->top_controls_manager()->ContentTopOffset());
 
   gfx::Vector2dF scroll_delta(0.f, 25.f);
   EXPECT_EQ(InputHandler::ScrollStarted,
@@ -2970,9 +2977,9 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsAspectRatio) {
   host_impl_->ScrollBy(gfx::Point(), scroll_delta);
   host_impl_->ScrollEnd();
 
-  EXPECT_EQ(scroll_delta.y(),
-            top_controls_height_ -
-                host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_FLOAT_EQ(scroll_delta.y(),
+                  top_controls_height_ -
+                      host_impl_->top_controls_manager()->ContentTopOffset());
 
   // Top controls were hidden by 25px so the inner viewport should have expanded
   // by that much.
@@ -2998,7 +3005,7 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsScrollOuterViewport) {
   DrawFrame();
 
   EXPECT_EQ(top_controls_height_,
-            host_impl_->active_tree()->total_top_controls_content_offset());
+            host_impl_->top_controls_manager()->ContentTopOffset());
 
   // Send a gesture scroll that will scroll the outer viewport, make sure the
   // top controls get scrolled.
@@ -3010,16 +3017,16 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsScrollOuterViewport) {
             host_impl_->CurrentlyScrollingLayer());
   host_impl_->ScrollEnd();
 
-  EXPECT_EQ(scroll_delta.y(),
-            top_controls_height_ -
-                host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_FLOAT_EQ(scroll_delta.y(),
+                  top_controls_height_ -
+                      host_impl_->top_controls_manager()->ContentTopOffset());
 
   scroll_delta = gfx::Vector2dF(0.f, 50.f);
   EXPECT_EQ(InputHandler::ScrollStarted,
             host_impl_->ScrollBegin(gfx::Point(), InputHandler::Gesture));
   host_impl_->ScrollBy(gfx::Point(), scroll_delta);
 
-  EXPECT_EQ(0, host_impl_->active_tree()->total_top_controls_content_offset());
+  EXPECT_EQ(0, host_impl_->top_controls_manager()->ContentTopOffset());
   EXPECT_EQ(host_impl_->OuterViewportScrollLayer(),
             host_impl_->CurrentlyScrollingLayer());
 
@@ -3036,8 +3043,8 @@ TEST_F(LayerTreeHostImplTopControlsTest, TopControlsScrollOuterViewport) {
   host_impl_->ScrollBy(gfx::Point(), scroll_delta);
 
   EXPECT_EQ(top_controls_height_,
-            host_impl_->active_tree()->total_top_controls_content_offset());
-  EXPECT_EQ(
+            host_impl_->top_controls_manager()->ContentTopOffset());
+  EXPECT_FLOAT_EQ(
       inner_viewport_offset.y() + (scroll_delta.y() + top_controls_height_),
       host_impl_->InnerViewportScrollLayer()->ScrollDelta().y());
 
@@ -3070,8 +3077,8 @@ TEST_F(LayerTreeHostImplTopControlsTest,
   host_impl_->top_controls_manager()->ScrollBegin();
   host_impl_->top_controls_manager()->ScrollBy(
       gfx::Vector2dF(0.f, scroll_increment_y));
-  EXPECT_EQ(-scroll_increment_y,
-            host_impl_->top_controls_manager()->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-scroll_increment_y,
+                  host_impl_->top_controls_manager()->ContentTopOffset());
   // Now that top controls have moved, expect the clip to resize.
   EXPECT_EQ(gfx::Size(viewport_size_.width(),
                       viewport_size_.height() + scroll_increment_y),
@@ -3080,8 +3087,8 @@ TEST_F(LayerTreeHostImplTopControlsTest,
   host_impl_->top_controls_manager()->ScrollBy(
       gfx::Vector2dF(0.f, scroll_increment_y));
   host_impl_->top_controls_manager()->ScrollEnd();
-  EXPECT_EQ(-2 * scroll_increment_y,
-            host_impl_->top_controls_manager()->ContentTopOffset());
+  EXPECT_FLOAT_EQ(-2 * scroll_increment_y,
+                  host_impl_->top_controls_manager()->ContentTopOffset());
   // Now that top controls have moved, expect the clip to resize.
   EXPECT_EQ(clip_size_, root_clip_ptr->bounds());
 
@@ -7439,9 +7446,8 @@ class LayerTreeHostImplWithTopControlsTest : public LayerTreeHostImplTest {
     settings.calculate_top_controls_position = true;
     CreateHostImpl(settings, CreateOutputSurface());
     host_impl_->active_tree()->set_top_controls_height(top_controls_height_);
-    host_impl_->active_tree()->set_top_controls_delta(top_controls_height_);
-    host_impl_->top_controls_manager()->SetTopControlsHeight(
-        top_controls_height_);
+    host_impl_->sync_tree()->set_top_controls_height(top_controls_height_);
+    host_impl_->active_tree()->SetCurrentTopControlsShownRatio(1.f);
   }
 
  protected:
@@ -7463,23 +7469,23 @@ TEST_F(LayerTreeHostImplWithTopControlsTest, TopControlsHeightIsCommitted) {
   host_impl_->CreatePendingTree();
   host_impl_->sync_tree()->set_top_controls_height(100);
   host_impl_->ActivateSyncTree();
-  EXPECT_EQ(100, host_impl_->top_controls_manager()->top_controls_height());
+  EXPECT_EQ(100, host_impl_->top_controls_manager()->TopControlsHeight());
 }
 
 TEST_F(LayerTreeHostImplWithTopControlsTest,
        TopControlsStayFullyVisibleOnHeightChange) {
   SetupScrollAndContentsLayers(gfx::Size(100, 100));
-  EXPECT_EQ(0.f, host_impl_->ControlsTopOffset());
+  EXPECT_EQ(0.f, host_impl_->top_controls_manager()->ControlsTopOffset());
 
   host_impl_->CreatePendingTree();
   host_impl_->sync_tree()->set_top_controls_height(0);
   host_impl_->ActivateSyncTree();
-  EXPECT_EQ(0.f, host_impl_->ControlsTopOffset());
+  EXPECT_EQ(0.f, host_impl_->top_controls_manager()->ControlsTopOffset());
 
   host_impl_->CreatePendingTree();
   host_impl_->sync_tree()->set_top_controls_height(50);
   host_impl_->ActivateSyncTree();
-  EXPECT_EQ(0.f, host_impl_->ControlsTopOffset());
+  EXPECT_EQ(0.f, host_impl_->top_controls_manager()->ControlsTopOffset());
 }
 
 TEST_F(LayerTreeHostImplWithTopControlsTest, TopControlsAnimationScheduling) {
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 80ccf14..0759425 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -4,6 +4,7 @@
 
 #include "cc/trees/layer_tree_impl.h"
 
+#include <algorithm>
 #include <limits>
 #include <set>
 
@@ -76,6 +77,7 @@ class LayerScrollOffsetDelegateProxy : public LayerImpl::ScrollOffsetDelegate {
 LayerTreeImpl::LayerTreeImpl(
     LayerTreeHostImpl* layer_tree_host_impl,
     scoped_refptr<SyncedProperty<ScaleGroup>> page_scale_factor,
+    scoped_refptr<SyncedTopControls> top_controls_shown_ratio,
     scoped_refptr<SyncedElasticOverscroll> elastic_overscroll)
     : layer_tree_host_impl_(layer_tree_host_impl),
       source_frame_number_(-1),
@@ -102,9 +104,7 @@ LayerTreeImpl::LayerTreeImpl(
       render_surface_layer_list_id_(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) {
+      top_controls_shown_ratio_(top_controls_shown_ratio) {
 }
 
 LayerTreeImpl::~LayerTreeImpl() {
@@ -210,20 +210,10 @@ void LayerTreeImpl::PushPropertiesTo(LayerTreeImpl* target_tree) {
 
   target_tree->PassSwapPromises(&swap_promise_list_);
 
-  // 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_ -
-                                     top_controls_height_delta;
-  target_tree->sent_top_controls_delta_ = 0.f;
+  target_tree->set_top_controls_shrink_blink_size(
+      top_controls_shrink_blink_size_);
+  target_tree->set_top_controls_height(top_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.
@@ -364,6 +354,48 @@ void LayerTreeImpl::PushPageScaleFactorAndLimits(const float* page_scale_factor,
     DidUpdatePageScale();
 }
 
+void LayerTreeImpl::set_top_controls_shrink_blink_size(bool shrink) {
+  if (top_controls_shrink_blink_size_ == shrink)
+    return;
+
+  top_controls_shrink_blink_size_ = shrink;
+  if (IsActiveTree())
+    layer_tree_host_impl_->UpdateViewportContainerSizes();
+}
+
+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();
+}
+
+bool LayerTreeImpl::SetCurrentTopControlsShownRatio(float ratio) {
+  ratio = std::max(ratio, 0.f);
+  ratio = std::min(ratio, 1.f);
+  return top_controls_shown_ratio_->SetCurrent(ratio);
+}
+
+void LayerTreeImpl::PushTopControlsFromMainThread(
+    float top_controls_shown_ratio) {
+  PushTopControls(&top_controls_shown_ratio);
+}
+
+void LayerTreeImpl::PushTopControls(const float* top_controls_shown_ratio) {
+  DCHECK(top_controls_shown_ratio || IsActiveTree());
+
+  if (top_controls_shown_ratio) {
+    DCHECK(!IsActiveTree() || !layer_tree_host_impl_->pending_tree());
+    top_controls_shown_ratio_->PushFromMainThread(*top_controls_shown_ratio);
+  }
+  if (IsActiveTree()) {
+    if (top_controls_shown_ratio_->PushPendingToActive())
+      layer_tree_host_impl_->DidChangeTopControlsPosition();
+  }
+}
+
 bool LayerTreeImpl::SetPageScaleFactorLimits(float min_page_scale_factor,
                                              float max_page_scale_factor) {
   if (min_page_scale_factor == min_page_scale_factor_ &&
@@ -451,12 +483,9 @@ void LayerTreeImpl::ApplySentScrollAndScaleDeltasFromAbortedCommit() {
   DCHECK(IsActiveTree());
 
   page_scale_factor()->AbortCommit();
+  top_controls_shown_ratio()->AbortCommit();
   elastic_overscroll()->AbortCommit();
 
-  top_controls_content_offset_ += sent_top_controls_delta_;
-  top_controls_delta_ -= sent_top_controls_delta_;
-  sent_top_controls_delta_ = 0.f;
-
   if (!root_layer())
     return;
 
diff --git a/cc/trees/layer_tree_impl.h b/cc/trees/layer_tree_impl.h
index 2329139..19bba86 100644
--- a/cc/trees/layer_tree_impl.h
+++ b/cc/trees/layer_tree_impl.h
@@ -55,6 +55,7 @@ struct RendererCapabilities;
 struct SelectionHandle;
 
 typedef std::vector<UIResourceRequest> UIResourceRequestQueue;
+typedef SyncedProperty<AdditionGroup<float>> SyncedTopControls;
 typedef SyncedProperty<AdditionGroup<gfx::Vector2dF>> SyncedElasticOverscroll;
 
 class CC_EXPORT LayerTreeImpl {
@@ -62,9 +63,11 @@ class CC_EXPORT LayerTreeImpl {
   static scoped_ptr<LayerTreeImpl> create(
       LayerTreeHostImpl* layer_tree_host_impl,
       scoped_refptr<SyncedProperty<ScaleGroup>> page_scale_factor,
+      scoped_refptr<SyncedTopControls> top_controls_shown_ratio,
       scoped_refptr<SyncedElasticOverscroll> elastic_overscroll) {
-    return make_scoped_ptr(new LayerTreeImpl(
-        layer_tree_host_impl, page_scale_factor, elastic_overscroll));
+    return make_scoped_ptr(
+        new LayerTreeImpl(layer_tree_host_impl, page_scale_factor,
+                          top_controls_shown_ratio, elastic_overscroll));
   }
   virtual ~LayerTreeImpl();
 
@@ -192,6 +195,13 @@ class CC_EXPORT LayerTreeImpl {
     return elastic_overscroll_.get();
   }
 
+  SyncedTopControls* top_controls_shown_ratio() {
+    return top_controls_shown_ratio_.get();
+  }
+  const SyncedTopControls* top_controls_shown_ratio() const {
+    return top_controls_shown_ratio_.get();
+  }
+
   // Updates draw properties and render surface layer list, as well as tile
   // priorities. Returns false if it was unable to update.
   bool UpdateDrawProperties();
@@ -303,36 +313,17 @@ class CC_EXPORT LayerTreeImpl {
   void RegisterPictureLayerImpl(PictureLayerImpl* layer);
   void UnregisterPictureLayerImpl(PictureLayerImpl* layer);
 
-  void set_top_controls_shrink_blink_size(bool shrink) {
-    top_controls_shrink_blink_size_ = shrink;
-  }
-  void set_top_controls_height(float height) { top_controls_height_ = height; }
-  void set_top_controls_content_offset(float offset) {
-    top_controls_content_offset_ = offset;
-  }
-  void set_top_controls_delta(float delta) {
-    top_controls_delta_ = delta;
-  }
-  void set_sent_top_controls_delta(float sent_delta) {
-    sent_top_controls_delta_ = sent_delta;
-  }
-
+  void set_top_controls_shrink_blink_size(bool shrink);
   bool top_controls_shrink_blink_size() const {
     return top_controls_shrink_blink_size_;
   }
-  float top_controls_height() const { return top_controls_height_; }
-  float top_controls_content_offset() const {
-    return top_controls_content_offset_;
-  }
-  float top_controls_delta() const {
-    return top_controls_delta_;
-  }
-  float sent_top_controls_delta() const {
-    return sent_top_controls_delta_;
-  }
-  float total_top_controls_content_offset() const {
-    return top_controls_content_offset_ + top_controls_delta_;
+  bool SetCurrentTopControlsShownRatio(float ratio);
+  float CurrentTopControlsShownRatio() const {
+    return top_controls_shown_ratio_->Current(IsActiveTree());
   }
+  void set_top_controls_height(float top_controls_height);
+  float top_controls_height() const { return top_controls_height_; }
+  void PushTopControlsFromMainThread(float top_controls_shown_ratio);
 
   void SetPendingPageScaleAnimation(
       scoped_ptr<PendingPageScaleAnimation> pending_animation);
@@ -342,6 +333,7 @@ class CC_EXPORT LayerTreeImpl {
   explicit LayerTreeImpl(
       LayerTreeHostImpl* layer_tree_host_impl,
       scoped_refptr<SyncedProperty<ScaleGroup>> page_scale_factor,
+      scoped_refptr<SyncedTopControls> top_controls_shown_ratio,
       scoped_refptr<SyncedElasticOverscroll> elastic_overscroll);
   void ProcessLayersRecursive(LayerImpl* current,
                               void (LayerImpl::*function)());
@@ -353,7 +345,7 @@ class CC_EXPORT LayerTreeImpl {
                                 float max_page_scale_factor);
   void DidUpdatePageScale();
   void HideInnerViewportScrollbarsIfNearMinimumScale();
-
+  void PushTopControls(const float* top_controls_shown_ratio);
   LayerTreeHostImpl* layer_tree_host_impl_;
   int source_frame_number_;
   scoped_ptr<LayerImpl> root_layer_;
@@ -416,11 +408,9 @@ class CC_EXPORT LayerTreeImpl {
 
   float top_controls_height_;
 
-  // The up-to-date content offset of the top controls, i.e. the amount that the
-  // web contents have been shifted down from the top of the device viewport.
-  float top_controls_content_offset_;
-  float top_controls_delta_;
-  float sent_top_controls_delta_;
+  // The amount that the top controls are shown from 0 (hidden) to 1 (fully
+  // shown).
+  scoped_refptr<SyncedTopControls> top_controls_shown_ratio_;
 
   scoped_ptr<PendingPageScaleAnimation> pending_page_scale_animation_;