Make LayerTreeHostClient::Animate take TimeTicks instead of double

This makes LayerTreeHostClient::Animate take a TimeTicks instead of a
double, moving the conversion to double from the caller of Animate to
wherever doubles are actually needed.

This avoids precision loss caused by converting from TimeTicks to
double and back again when TimeTicks are actually needed (as in
LayerTreeHostClientForTesting::Animate) fixing the suspected cause
of flakiness in LayerTreeHostAnimationTestFrozenAnimationTickTime.

R=danakj,jamesr
TBR=sky

BUG=341517

Review URL: https://codereview.chromium.org/153633006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249660 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 4 insertions, 3 deletions

diff --git a/mojo/examples/compositor_app/compositor_host.cc b/mojo/examples/compositor_app/compositor_host.cc
index 0760910..8f5e47c 100644
--- a/mojo/examples/compositor_app/compositor_host.cc
+++ b/mojo/examples/compositor_app/compositor_host.cc
@@ -54,10 +54,11 @@ void CompositorHost::SetupScene() {
 void CompositorHost::WillBeginMainFrame(int frame_id) {}
 void CompositorHost::DidBeginMainFrame() {}
 
-void CompositorHost::Animate(double frame_begin_time) {
+void CompositorHost::Animate(base::TimeTicks frame_begin_time) {
   // TODO(jamesr): Should use cc's animation system.
   static const double kDegreesPerSecond = 70.0;
-  double child_rotation_degrees = kDegreesPerSecond * frame_begin_time;
+  double time_in_seconds = (frame_begin_time - base::TimeTicks()).InSecondsF();
+  double child_rotation_degrees = kDegreesPerSecond * time_in_seconds;
   gfx::Transform child_transform;
   child_transform.Translate(200, 200);
   child_transform.Rotate(child_rotation_degrees);
diff --git a/mojo/examples/compositor_app/compositor_host.h b/mojo/examples/compositor_app/compositor_host.h
index a7a96ea..97f5b14 100644
--- a/mojo/examples/compositor_app/compositor_host.h
+++ b/mojo/examples/compositor_app/compositor_host.h
@@ -31,7 +31,7 @@ class CompositorHost : public cc::LayerTreeHostClient {
   // cc::LayerTreeHostClient implementation.
   virtual void WillBeginMainFrame(int frame_id) OVERRIDE;
   virtual void DidBeginMainFrame() OVERRIDE;
-  virtual void Animate(double frame_begin_time) OVERRIDE;
+  virtual void Animate(base::TimeTicks frame_begin_time) OVERRIDE;
   virtual void Layout() OVERRIDE;
   virtual void ApplyScrollAndScale(const gfx::Vector2d& scroll_delta,
                                    float page_scale) OVERRIDE;