cc: Introduce BeginFrame sequence numbers and acknowledgements.

cc/scheduler/scheduler_unittest.cc

Index: cc/scheduler/scheduler_unittest.cc
diff --git a/cc/scheduler/scheduler_unittest.cc b/cc/scheduler/scheduler_unittest.cc
index ace12c64bdc1c3a2d44030f153e2e4c3868f8958..1f711079ea0c4e2b5489fd6619855c8395bab222 100644
--- a/cc/scheduler/scheduler_unittest.cc
+++ b/cc/scheduler/scheduler_unittest.cc
@@ -236,7 +236,8 @@ class SchedulerTest : public testing::Test {
   SchedulerTest()
       : now_src_(new base::SimpleTestTickClock()),
         task_runner_(new OrderedSimpleTaskRunner(now_src_.get(), true)),
-        fake_external_begin_frame_source_(nullptr) {
+        fake_external_begin_frame_source_(nullptr),
+        next_begin_frame_number_(BeginFrameArgs::kStartingFrameNumber) {
     now_src_->Advance(base::TimeDelta::FromMicroseconds(10000));
     // A bunch of tests require NowTicks()
     // to be > BeginFrameArgs::DefaultInterval()
@@ -405,8 +406,9 @@ class SchedulerTest : public testing::Test {
     // Creep the time forward so that any BeginFrameArgs is not equal to the
     // last one otherwise we violate the BeginFrameSource contract.
     now_src_->Advance(BeginFrameArgs::DefaultInterval());
-    BeginFrameArgs args =
-        CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, now_src());
+    BeginFrameArgs args = CreateBeginFrameArgsForTesting(
+        BEGINFRAME_FROM_HERE, fake_external_begin_frame_source_->source_id(),
+        next_begin_frame_number_++, now_src());
     fake_external_begin_frame_source_->TestOnBeginFrame(args);
     return args;
   }
@@ -435,6 +437,7 @@ class SchedulerTest : public testing::Test {
   std::unique_ptr<FakeSchedulerClient> client_;
   std::unique_ptr<TestScheduler> scheduler_;
   FakeCompositorTimingHistory* fake_compositor_timing_history_;
+  uint64_t next_begin_frame_number_;
 };
 
 TEST_F(SchedulerTest, InitializeCompositorFrameSinkDoesNotBeginImplFrame) {
@@ -1332,8 +1335,9 @@ TEST_F(SchedulerTest, MainFrameNotSkippedAfterLateBeginFrame) {
 
   // Advance frame and create a begin frame.
   now_src_->Advance(BeginFrameArgs::DefaultInterval());
-  BeginFrameArgs args =
-      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, now_src());
+  BeginFrameArgs args = CreateBeginFrameArgsForTesting(
+      BEGINFRAME_FROM_HERE, fake_external_begin_frame_source_->source_id(),
+      next_begin_frame_number_++, now_src());
 
   // Deliver this begin frame super late.
   now_src_->Advance(BeginFrameArgs::DefaultInterval() * 100);