cc: Adding BeginFrameTracker object and removing Now() from LTHI.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index ea8a29f46560dbaf88d13c08f9247dd7c3da857a..951d95179700d4f85b33ce24545c3c8e93b44bb9 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -71,7 +71,6 @@
 #include "cc/trees/tree_synchronizer.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "gpu/GLES2/gl2extchromium.h"
-#include "ui/gfx/frame_time.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/geometry/vector2d_conversions.h"
@@ -220,7 +219,6 @@ LayerTreeHostImpl::LayerTreeHostImpl(
       device_scale_factor_(1.f),
       overhang_ui_resource_id_(0),
       resourceless_software_draw_(false),
-      begin_impl_frame_interval_(BeginFrameArgs::DefaultInterval()),
       animation_registrar_(AnimationRegistrar::Create()),
       rendering_stats_instrumentation_(rendering_stats_instrumentation),
       micro_benchmark_controller_(this),
@@ -374,6 +372,9 @@ bool LayerTreeHostImpl::CanDraw() const {
 }
 
 void LayerTreeHostImpl::Animate(base::TimeTicks monotonic_time) {
+  // DCHECK(!current_begin_frame_args_.HasFinished());
+  // DCHECK(monotonic_time == current_begin_frame_args_.Get().frame_time)
+  //  << "Called animate with unknown frame time!?";
   if (input_handler_client_)
     input_handler_client_->Animate(monotonic_time);
   AnimatePageScale(monotonic_time);
@@ -1632,11 +1633,7 @@ bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
 }
 
 void LayerTreeHostImpl::WillBeginImplFrame(const BeginFrameArgs& args) {
-  // Sample the frame time now. This time will be used for updating animations
-  // when we draw.
-  UpdateCurrentBeginFrameArgs(args);
-  // Cache the begin impl frame interval
-  begin_impl_frame_interval_ = args.interval;
+  current_begin_frame_args_.Start(args);
 
   if (required_for_draw_tile_is_top_of_raster_queue_) {
     // Optimistically schedule a draw, as a tile required for draw is at the top
@@ -2409,7 +2406,7 @@ InputHandler::ScrollStatus LayerTreeHostImpl::ScrollAnimated(
 
     curve->UpdateTarget(
         animation->TrimTimeToCurrentIteration(
-                       CurrentBeginFrameArgs().frame_time).InSecondsF(),
+                       current_begin_frame_args_.Get().frame_time).InSecondsF(),
         new_target);
 
     return ScrollStarted;
@@ -3224,26 +3221,24 @@ TreePriority LayerTreeHostImpl::GetTreePriority() const {
 
 void LayerTreeHostImpl::UpdateCurrentBeginFrameArgs(
     const BeginFrameArgs& args) {
-  DCHECK(!current_begin_frame_args_.IsValid());
-  current_begin_frame_args_ = args;
-  // TODO(skyostil): Stop overriding the frame time once the usage of frame
-  // timing is unified.
-  current_begin_frame_args_.frame_time = gfx::FrameTime::Now();
+  current_begin_frame_args_.Start(args);
 }
 
 void LayerTreeHostImpl::ResetCurrentBeginFrameArgsForNextFrame() {
-  current_begin_frame_args_ = BeginFrameArgs();
+  current_begin_frame_args_.Finish();

[brianderson, 2014/12/18 02:01:38]

I forget why we need to reset the current args. Can we just keep them valid
until the next WillBeginImplFrame?

[mithro-old, 2014/12/18 17:22:41]

See my reasoning else were. I think the fact that even after reset we still
returned BeginFrameArgs has lead to some very bad code which the logic was
trying to prevent from existing in the first place.

 }
 
 BeginFrameArgs LayerTreeHostImpl::CurrentBeginFrameArgs() const {
-  // Try to use the current frame time to keep animations non-jittery.  But if
-  // we're not in a frame (because this is during an input event or a delayed
-  // task), fall back to physical time.  This should still be monotonic.
-  if (current_begin_frame_args_.IsValid())
-    return current_begin_frame_args_;
-  return BeginFrameArgs::Create(
-      BEGINFRAME_FROM_HERE, gfx::FrameTime::Now(), base::TimeTicks(),
-      BeginFrameArgs::DefaultInterval(), BeginFrameArgs::NORMAL);
+  // TODO(mithro): Remove this section once all calls to CurrentBeginFrameArgs
+  // which happens outside frame rendering are fixed.
+  if (current_begin_frame_args_.HasFinished()) {
+    return current_begin_frame_args_.Last();
+  }
+  return current_begin_frame_args_.Get();
+}
+
+base::TimeDelta LayerTreeHostImpl::CurrentBeginFrameInterval() const {
+  return current_begin_frame_args_.Interval();
 }
 
 scoped_refptr<base::debug::ConvertableToTraceFormat>