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

cc/test/scheduler_test_common.h

Index: cc/test/scheduler_test_common.h
diff --git a/cc/test/scheduler_test_common.h b/cc/test/scheduler_test_common.h
index a2982ee5fdaedb8ea8faafea30765337bfcd202b..633289ba3ff729cf5f909d0201b2dd0410185f46 100644
--- a/cc/test/scheduler_test_common.h
+++ b/cc/test/scheduler_test_common.h
@@ -184,6 +184,7 @@
 
   BeginFrameSource& frame_source() { return *frame_source_; }
   bool FrameProductionThrottled() { return throttle_frame_production_; }
+  BeginFrameArgs begin_impl_frame_args() { return begin_impl_frame_args_; }
 
   ~TestScheduler() override;
 
@@ -192,10 +193,6 @@
     if (settings_.impl_side_painting) {
       NotifyReadyToActivate();
     }
-  }
-
-  base::TimeDelta BeginImplFrameInterval() {
-    return begin_impl_frame_tracker_.Interval();
   }
 
  protected: