Gradient overlay for constrained window

ui/base/animation/linear_animation.cc

Index: ui/base/animation/linear_animation.cc
diff --git a/ui/base/animation/linear_animation.cc b/ui/base/animation/linear_animation.cc
index 60054d9cb78ed2095dbc02fd7d9d1b69d137b68b..33bd1d1a4818effafad12a00056cdb28048aaa64 100644
--- a/ui/base/animation/linear_animation.cc
+++ b/ui/base/animation/linear_animation.cc
@@ -45,6 +45,14 @@ double LinearAnimation::GetCurrentValue() const {
   return state_;
 }
 
+void LinearAnimation::SetCurrentValue(double new_value) {
+  new_value = std::max(0.0, std::min(1.0, new_value));
+  base::TimeDelta time_delta = base::TimeDelta::FromMicroseconds(
+      duration_.InMicroseconds() * (new_value - state_));
+  SetStartTime(start_time() - time_delta);
+  state_ = new_value;
+}
+
 void LinearAnimation::End() {
   if (!is_animating())
     return;
@@ -79,6 +87,10 @@ void LinearAnimation::Step(base::TimeTicks time_now) {
     Stop();
 }
 
+void LinearAnimation::AnimationStarted() {
+  state_ = 0.0;
+}
+
 void LinearAnimation::AnimationStopped() {
   if (!in_end_)
     return;