Update from https://crrev.com/316786

cc/input/top_controls_manager.cc

Index: cc/input/top_controls_manager.cc
diff --git a/cc/input/top_controls_manager.cc b/cc/input/top_controls_manager.cc
index 1615d7f2d3875e4766bb55f884e166caa7d380b9..615afb07056800b92d55ad38807fec7ce2212c65 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;