Early terminate flings when scrolling impossible

content/child/fling_animator_impl_android.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #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"
 #include "ui/gfx/android/view_configuration.h"
 #include "ui/gfx/frame_time.h"
 #include "ui/gfx/vector2d.h"
 
 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;
   config.fling_friction = gfx::ViewConfiguration::GetScrollFriction();
   return config;
 }
 
 }  // namespace
 
 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
   // Instead, use the largest possible bounds for minX/maxX/minY/maxY. The
   // compositor will ignore any attempt to scroll beyond the end of the page.
 
   DCHECK(velocity.x() || velocity.y());
   if (is_active_)
     CancelFling();
 
@@ skipping 23 matching lines @@
                               blink::WebGestureCurveTarget* target) {
   // Historically, Android's Scroller used |currentAnimationTimeMillis()|,
   // which is equivalent to gfx::FrameTime::Now().  In practice, this produces
   // smoother results than using |time|, so continue using FrameTime::Now().
   // TODO(jdduke): Use |time| upon resolution of crbug.com/345459.
   if (!scroller_.ComputeScrollOffset(gfx::FrameTime::Now())) {
     is_active_ = false;
     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(
     const blink::WebFloatPoint& velocity,
     const blink::WebSize&) {
   FlingAnimatorImpl* gesture_curve = new FlingAnimatorImpl();
   gesture_curve->StartFling(velocity);
   return gesture_curve;
 }
 
 }  // namespace content