Use mockable time in CompositorFrameReportingController

This CL adds the possibility to inject a base::TickClock* into
CompositorFrameReportingController, so its timing can be mocked by
tests. CompositorFrameReportingControllerTest is also updated to make
use of this.

Bug: 1054009,1057193
Change-Id: I6ece91efe32395a37c14cd4ca4c59da9f2e05da0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2159894Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#762104}

cc/metrics/compositor_frame_reporting_controller.cc

@@ -49,7 +49,7 @@ CompositorFrameReportingController::SubmittedCompositorFrame::
     SubmittedCompositorFrame(SubmittedCompositorFrame&& other) = default;
 
 base::TimeTicks CompositorFrameReportingController::Now() const {
-  return base::TimeTicks::Now();
+  return tick_clock_->NowTicks();
 }
 
 bool CompositorFrameReportingController::HasReporterAt(

cc/metrics/compositor_frame_reporting_controller.h

@@ -8,6 +8,7 @@
 #include <memory>
 #include <vector>
 
+#include "base/time/default_tick_clock.h"
 #include "base/time/time.h"
 #include "cc/cc_export.h"
 #include "cc/metrics/compositor_frame_reporter.h"
@@ -77,6 +78,10 @@ class CC_EXPORT CompositorFrameReportingController {
   virtual void AddActiveTracker(FrameSequenceTrackerType type);
   virtual void RemoveActiveTracker(FrameSequenceTrackerType type);
 
+  void set_tick_clock(const base::TickClock* tick_clock) {
+    tick_clock_ = tick_clock;
+  }
+
   std::unique_ptr<CompositorFrameReporter>* reporters() { return reporters_; }
 
  protected:
@@ -120,6 +125,8 @@ class CC_EXPORT CompositorFrameReportingController {
   // DO NOT reorder this line and the one above. The latency_ukm_reporter_ must
   // outlive the objects in |submitted_compositor_frames_|.
   base::circular_deque<SubmittedCompositorFrame> submitted_compositor_frames_;
+
+  const base::TickClock* tick_clock_ = base::DefaultTickClock::GetInstance();
 };
 }  // namespace cc
 

cc/metrics/compositor_frame_reporting_controller_unittest.cc

@@ -10,6 +10,7 @@
 #include "base/macros.h"
 #include "base/strings/strcat.h"
 #include "base/test/metrics/histogram_tester.h"
+#include "base/test/simple_test_tick_clock.h"
 #include "cc/input/scroll_input_type.h"
 #include "cc/metrics/event_metrics.h"
 #include "components/viz/common/frame_timing_details.h"
@@ -56,6 +57,8 @@ class TestCompositorFrameReportingController
 class CompositorFrameReportingControllerTest : public testing::Test {
  public:
   CompositorFrameReportingControllerTest() : current_id_(1, 1) {
+    test_tick_clock_.SetNowTicks(base::TimeTicks::Now());
+    reporting_controller_.set_tick_clock(&test_tick_clock_);
     args_ = SimulateBeginFrameArgs(current_id_);
   }
 
@@ -137,20 +140,21 @@ class CompositorFrameReportingControllerTest : public testing::Test {
   }
 
   base::TimeTicks AdvanceNowByMs(int64_t advance_ms) {
-    now_ += base::TimeDelta::FromMicroseconds(advance_ms);
-    return now_;
+    test_tick_clock_.Advance(base::TimeDelta::FromMicroseconds(advance_ms));
+    return test_tick_clock_.NowTicks();
   }
 
  protected:
+  // This should be defined before |reporting_controller_| so it is created
+  // before and destroyed after that.
+  base::SimpleTestTickClock test_tick_clock_;
+
   TestCompositorFrameReportingController reporting_controller_;
   viz::BeginFrameArgs args_;
   viz::BeginFrameId current_id_;
   viz::BeginFrameId last_activated_id_;
   base::TimeTicks begin_main_start_;
   viz::FrameTokenGenerator next_token_;
-
- private:
-  base::TimeTicks now_ = base::TimeTicks::Now();
 };
 
 TEST_F(CompositorFrameReportingControllerTest, ActiveReporterCounts) {