Revert of 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 a164e8c85dd4d8489148c51bf2e9b5c347c3e9ee..eea6236ab6280627eba8b0e6a3e251c90781b26d 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -76,6 +76,7 @@
 #include "cc/trees/tree_synchronizer.h"
 #include "gpu/GLES2/gl2extchromium.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
+#include "ui/gfx/frame_time.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/scroll_offset.h"
 #include "ui/gfx/geometry/size_conversions.h"
@@ -189,7 +190,6 @@
     int id)
     : client_(client),
       proxy_(proxy),
-      current_begin_frame_tracker_(BEGINFRAMETRACKER_FROM_HERE),
       content_is_suitable_for_gpu_rasterization_(true),
       has_gpu_rasterization_trigger_(false),
       use_gpu_rasterization_(false),
@@ -220,6 +220,7 @@
       max_memory_needed_bytes_(0),
       device_scale_factor_(1.f),
       resourceless_software_draw_(false),
+      begin_impl_frame_interval_(BeginFrameArgs::DefaultInterval()),
       animation_registrar_(AnimationRegistrar::Create()),
       rendering_stats_instrumentation_(rendering_stats_instrumentation),
       micro_benchmark_controller_(this),
@@ -392,10 +393,6 @@
 }
 
 void LayerTreeHostImpl::Animate(base::TimeTicks monotonic_time) {
-  // mithro(TODO): Enable these checks.
-  // DCHECK(!current_begin_frame_tracker_.HasFinished());
-  // DCHECK(monotonic_time == current_begin_frame_tracker_.Current().frame_time)
-  //  << "Called animate with unknown frame time!?";
   if (input_handler_client_)
     input_handler_client_->Animate(monotonic_time);
   AnimatePageScale(monotonic_time);
@@ -1672,7 +1669,16 @@
 }
 
 void LayerTreeHostImpl::WillBeginImplFrame(const BeginFrameArgs& args) {
-  current_begin_frame_tracker_.Start(args);
+  // Sample the frame time now. This time will be used for updating animations
+  // when we draw.
+  DCHECK(!current_begin_frame_args_.IsValid());
+  current_begin_frame_args_ = args;
+  // TODO(mithro): Stop overriding the frame time once the usage of frame
+  // timing is unified.
+  current_begin_frame_args_.frame_time = gfx::FrameTime::Now();
+
+  // Cache the begin impl frame interval
+  begin_impl_frame_interval_ = args.interval;
 
   if (is_likely_to_require_a_draw_) {
     // Optimistically schedule a draw. This will let us expect the tile manager
@@ -1686,7 +1692,8 @@
 }
 
 void LayerTreeHostImpl::DidFinishImplFrame() {
-  current_begin_frame_tracker_.Finish();
+  DCHECK(current_begin_frame_args_.IsValid());
+  current_begin_frame_args_ = BeginFrameArgs();
 }
 
 void LayerTreeHostImpl::UpdateViewportContainerSizes() {
@@ -3109,9 +3116,8 @@
     VideoFrameController* controller) {
   bool was_empty = video_frame_controllers_.empty();
   video_frame_controllers_.insert(controller);
-  if (current_begin_frame_tracker_.DangerousMethodHasStarted() &&
-      !current_begin_frame_tracker_.DangerousMethodHasFinished())
-    controller->OnBeginFrame(current_begin_frame_tracker_.Current());
+  if (current_begin_frame_args_.IsValid())
+    controller->OnBeginFrame(current_begin_frame_args_);
   if (was_empty)
     client_->SetVideoNeedsBeginFrames(true);
 }
@@ -3138,13 +3144,14 @@
 }
 
 BeginFrameArgs LayerTreeHostImpl::CurrentBeginFrameArgs() const {
-  // TODO(mithro): Replace call with current_begin_frame_tracker_.Current()
-  // once all calls which happens outside impl frames are fixed.
-  return current_begin_frame_tracker_.DangerousMethodCurrentOrLast();
-}
-
-base::TimeDelta LayerTreeHostImpl::CurrentBeginFrameInterval() const {
-  return current_begin_frame_tracker_.Interval();
+  // 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);
 }
 
 scoped_refptr<base::trace_event::ConvertableToTraceFormat>