Early terminate flings when scrolling impossible

content/child/fling_animator_impl_android.cc

Index: content/child/fling_animator_impl_android.cc
diff --git a/content/child/fling_animator_impl_android.cc b/content/child/fling_animator_impl_android.cc
index 235f920b48f1cecf757c86ed5c79dd75956deb61..e2921445defe6ff1414fed39a5483e554091a0c6 100644
--- a/content/child/fling_animator_impl_android.cc
+++ b/content/child/fling_animator_impl_android.cc
@@ -4,6 +4,7 @@
 
 #include "content/child/fling_animator_impl_android.h"
 
+#include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "third_party/WebKit/public/platform/WebFloatSize.h"
 #include "third_party/WebKit/public/platform/WebGestureCurveTarget.h"
@@ -15,6 +16,8 @@ namespace content {
 
 namespace {
 
+const char* kCurveName = "FlingAnimatorImpl";

[jochen (gone - plz use gerrit), 2014/03/31 09:59:10]

why do you declare a variable for this but none of the other string constants?

[jdduke (slow), 2014/03/31 15:41:43]

I added the trace to mimic what was done in touch_fling_gesture_curve.cc, where
they also declare the string constant as a variable.  However, it appears we
already have an async fling trace sequence in input_handler_proxy.cc, so this is
redundant and I see no reason to have this, I'll remove.

+
 gfx::Scroller::Config GetScrollerConfig() {
   gfx::Scroller::Config config;
   config.flywheel_enabled = false;
@@ -26,9 +29,14 @@ gfx::Scroller::Config GetScrollerConfig() {
 
 FlingAnimatorImpl::FlingAnimatorImpl()
     : is_active_(false),
-      scroller_(GetScrollerConfig()) {}
+      scroller_(GetScrollerConfig()) {
+  TRACE_EVENT_ASYNC_BEGIN1(
+      "input", "GestureAnimation", this, "curve", kCurveName);
+}
 
-FlingAnimatorImpl::~FlingAnimatorImpl() {}
+FlingAnimatorImpl::~FlingAnimatorImpl() {
+  TRACE_EVENT_ASYNC_END0("input", "GestureAnimation", this);
+}
 
 void FlingAnimatorImpl::StartFling(const gfx::PointF& velocity) {
   // No bounds on the fling. See http://webkit.org/b/96403
@@ -72,17 +80,15 @@ bool FlingAnimatorImpl::apply(double /* time */,
     return false;
   }
 
-  target->notifyCurrentFlingVelocity(blink::WebFloatSize(
-      scroller_.GetCurrVelocityX(), scroller_.GetCurrVelocityY()));
-
   gfx::PointF current_position(scroller_.GetCurrX(), scroller_.GetCurrY());
   gfx::Vector2dF scroll_amount(current_position - last_position_);
   last_position_ = current_position;
 
   // scrollBy() could delete this curve if the animation is over, so don't touch
   // any member variables after making that call.
-  target->scrollBy(blink::WebFloatSize(scroll_amount));
-  return true;
+  return target->scrollBy(blink::WebFloatSize(scroll_amount),
+                          blink::WebFloatSize(scroller_.GetCurrVelocityX(),
+                                              scroller_.GetCurrVelocityY()));
 }
 
 FlingAnimatorImpl* FlingAnimatorImpl::CreateAndroidGestureCurve(