Revert of Remove a frame of delay on main-thread FlingStart.

third_party/WebKit/Source/platform/exported/WebActiveGestureAnimation.cpp

Index: third_party/WebKit/Source/platform/exported/WebActiveGestureAnimation.cpp
diff --git a/third_party/WebKit/Source/platform/exported/WebActiveGestureAnimation.cpp b/third_party/WebKit/Source/platform/exported/WebActiveGestureAnimation.cpp
index aa3070dc4770677cba78758327d6bf758a03d090..a149026038ba9d64ea76b3c6598f0226dff8302e 100644
--- a/third_party/WebKit/Source/platform/exported/WebActiveGestureAnimation.cpp
+++ b/third_party/WebKit/Source/platform/exported/WebActiveGestureAnimation.cpp
@@ -33,12 +33,20 @@
 namespace blink {
 
 std::unique_ptr<WebActiveGestureAnimation>
+WebActiveGestureAnimation::CreateAtAnimationStart(
+    std::unique_ptr<WebGestureCurve> curve,
+    WebGestureCurveTarget* target) {
+  return WTF::WrapUnique(
+      new WebActiveGestureAnimation(std::move(curve), target, 0, true));
+}
+
+std::unique_ptr<WebActiveGestureAnimation>
 WebActiveGestureAnimation::CreateWithTimeOffset(
     std::unique_ptr<WebGestureCurve> curve,
     WebGestureCurveTarget* target,
     double start_time) {
-  return WTF::WrapUnique(
-      new WebActiveGestureAnimation(std::move(curve), target, start_time));
+  return WTF::WrapUnique(new WebActiveGestureAnimation(std::move(curve), target,
+                                                       start_time, false));
 }
 
 WebActiveGestureAnimation::~WebActiveGestureAnimation() {}
@@ -46,10 +54,18 @@
 WebActiveGestureAnimation::WebActiveGestureAnimation(
     std::unique_ptr<WebGestureCurve> curve,
     WebGestureCurveTarget* target,
-    double start_time)
-    : start_time_(start_time), curve_(std::move(curve)), target_(target) {}
+    double start_time,
+    bool waiting_for_first_tick)
+    : start_time_(start_time),
+      waiting_for_first_tick_(waiting_for_first_tick),
+      curve_(std::move(curve)),
+      target_(target) {}
 
 bool WebActiveGestureAnimation::Animate(double time) {
+  if (waiting_for_first_tick_) {
+    start_time_ = time;
+    waiting_for_first_tick_ = false;
+  }
   // All WebGestureCurves assume zero-based time, so we subtract
   // the animation start time before passing to the curve.
   return curve_->Apply(time - start_time_, target_);