Reduce composited smooth scroll latency by a frame (also fixes latency UMAs).

cc/animation/animation_host_unittest.cc

Index: cc/animation/animation_host_unittest.cc
diff --git a/cc/animation/animation_host_unittest.cc b/cc/animation/animation_host_unittest.cc
index 4ae691a64e25e88c92bbdbfcd443a2b5e1e93dde..fdaefc7ba09c713339196697f333d9e82e18ebcd 100644
--- a/cc/animation/animation_host_unittest.cc
+++ b/cc/animation/animation_host_unittest.cc
@@ -87,7 +87,8 @@ TEST_F(AnimationHostTest, ImplOnlyScrollAnimationUpdateTargetIfDetached) {
   gfx::ScrollOffset target_offset(0., 2.);
   gfx::ScrollOffset current_offset(0., 1.);
   host_impl_->ImplOnlyScrollAnimationCreate(element_id_, target_offset,
-                                            current_offset, base::TimeDelta());
+                                            current_offset, base::TimeDelta(),
+                                            base::TimeDelta());
 
   gfx::Vector2dF scroll_delta(0, 0.5);
   gfx::ScrollOffset max_scroll_offset(0., 3.);