Provision to start base::SimpleTestTickClock at initial ticks

cc/scheduler/begin_frame_source_unittest.cc

Index: cc/scheduler/begin_frame_source_unittest.cc
diff --git a/cc/scheduler/begin_frame_source_unittest.cc b/cc/scheduler/begin_frame_source_unittest.cc
index 1f85622878e91680efd7f5ea56402c3653d81ada..0ae26ce38557b573dd38487c808441cbe280b776 100644
--- a/cc/scheduler/begin_frame_source_unittest.cc
+++ b/cc/scheduler/begin_frame_source_unittest.cc
@@ -343,7 +343,8 @@ class BackToBackBeginFrameSourceTest : public ::testing::Test {
 
   void SetUp() override {
     now_src_.reset(new base::SimpleTestTickClock());
-    now_src_->Advance(base::TimeDelta::FromMicroseconds(1000));
+    // SimpleTestTickClock starts at 1 microsecond, advance to 1000
+    now_src_->Advance(base::TimeDelta::FromMicroseconds(999));

[Sami, 2015/06/18 20:57:43]

It feels like having two constructor for SimpleTestTickClock would help to avoid
cases like these. One would initialize it to zero and the other would take a
TimeTicks value to initialize to. WDYT?

[Ankur Verma, 2015/06/30 09:19:26]

Done.

     task_runner_ =
         make_scoped_refptr(new OrderedSimpleTaskRunner(now_src_.get(), false));
     task_runner_->SetRunTaskLimit(1);