Revert of Show Overlay Scrollbar when GestureScrollUpdate

cc/input/scrollbar_animation_controller.cc

Index: cc/input/scrollbar_animation_controller.cc
diff --git a/cc/input/scrollbar_animation_controller.cc b/cc/input/scrollbar_animation_controller.cc
index 576ec2a4318ce93d1955db96d7a206c844e5b54b..08bb917242a78c0b0c3a736dc4592fb87e681005 100644
--- a/cc/input/scrollbar_animation_controller.cc
+++ b/cc/input/scrollbar_animation_controller.cc
@@ -53,7 +53,6 @@ ScrollbarAnimationController::ScrollbarAnimationController(
       scroll_gesture_has_scrolled_(false),
       opacity_(0.0f),
       fade_out_duration_(fade_out_duration),
-      show_scrollbars_on_scroll_gesture_(false),
       need_thinning_animation_(false),
       weak_factory_(this) {
   ApplyOpacityToScrollbars(0.0f);
@@ -78,7 +77,6 @@ ScrollbarAnimationController::ScrollbarAnimationController(
       scroll_gesture_has_scrolled_(false),
       opacity_(0.0f),
       fade_out_duration_(fade_out_duration),
-      show_scrollbars_on_scroll_gesture_(true),
       need_thinning_animation_(true),
       weak_factory_(this) {
   vertical_controller_ = SingleScrollbarAnimationControllerThinning::Create(
@@ -168,32 +166,17 @@ float ScrollbarAnimationController::AnimationProgressAtTime(
   return std::max(std::min(progress, 1.f), 0.f);
 }
 
-void ScrollbarAnimationController::RunAnimationFrame(float progress) {
-  ApplyOpacityToScrollbars(1.f - progress);
-  if (progress == 1.f)
-    StopAnimation();
-}
-
 void ScrollbarAnimationController::DidScrollBegin() {
   currently_scrolling_ = true;
 }
 
-void ScrollbarAnimationController::DidScrollEnd() {
-  bool has_scrolled = scroll_gesture_has_scrolled_;
-  scroll_gesture_has_scrolled_ = false;
-
-  currently_scrolling_ = false;
-
-  // We don't fade out scrollbar if they need thinning animation and mouse is
-  // near.
-  if (need_thinning_animation_ && MouseIsNearAnyScrollbar())
-    return;
-
-  if (has_scrolled)
-    PostDelayedFadeOut(false);
+void ScrollbarAnimationController::RunAnimationFrame(float progress) {
+  ApplyOpacityToScrollbars(1.f - progress);
+  if (progress == 1.f)
+    StopAnimation();
 }
 
-void ScrollbarAnimationController::DidScrollUpdate() {
+void ScrollbarAnimationController::DidScrollUpdate(bool on_resize) {
   if (need_thinning_animation_ && Captured())
     return;
 
@@ -205,7 +188,7 @@ void ScrollbarAnimationController::DidScrollUpdate() {
     // We don't fade out scrollbar if they need thinning animation and mouse is
     // near.
     if (!need_thinning_animation_ || !MouseIsNearAnyScrollbar())
-      PostDelayedFadeOut(false);
+      PostDelayedFadeOut(on_resize);
   } else {
     scroll_gesture_has_scrolled_ = true;
   }
@@ -218,17 +201,19 @@ void ScrollbarAnimationController::DidScrollUpdate() {
   }
 }
 
-void ScrollbarAnimationController::WillUpdateScroll() {
-  if (show_scrollbars_on_scroll_gesture_)
-    DidScrollUpdate();
-}
+void ScrollbarAnimationController::DidScrollEnd() {
+  bool has_scrolled = scroll_gesture_has_scrolled_;
+  scroll_gesture_has_scrolled_ = false;
 
-void ScrollbarAnimationController::DidResize() {
-  StopAnimation();
-  Show();
-  // We should use the gesture delay rather than the resize delay if we're in a
-  // gesture scroll, even if it is resizing.
-  PostDelayedFadeOut(!currently_scrolling_);
+  currently_scrolling_ = false;
+
+  // We don't fade out scrollbar if they need thinning animation and mouse is
+  // near.
+  if (need_thinning_animation_ && MouseIsNearAnyScrollbar())
+    return;
+
+  if (has_scrolled)
+    PostDelayedFadeOut(false);
 }
 
 void ScrollbarAnimationController::DidMouseDown() {