Add a task_scheduler tracing category which will record an extra event per task.

base/sequence_token_unittest.cc

Index: base/sequence_token_unittest.cc
diff --git a/base/sequence_token_unittest.cc b/base/sequence_token_unittest.cc
index 23e6283e9c2f7cda8f1ad674b62fbab28794bce2..b0e69de42bc707d3c1d1f5950fd0573539c32474 100644
--- a/base/sequence_token_unittest.cc
+++ b/base/sequence_token_unittest.cc
@@ -62,6 +62,14 @@ TEST(SequenceTokenTest, GetForCurrentThread) {
   EXPECT_FALSE(SequenceToken::GetForCurrentThread().IsValid());
 }
 
+TEST(SequenceTokenTest, ToInternalValue) {
+  const SequenceToken token1 = SequenceToken::Create();
+  const SequenceToken token2 = SequenceToken::Create();
+
+  // Confirm that internal values are unique.
+  EXPECT_NE(token1.ToInternalValue(), token2.ToInternalValue());
+}
+
 // Expect a default-constructed TaskToken to be invalid and not equal to
 // another invalid TaskToken.
 TEST(TaskTokenTest, InvalidDefaultConstructed) {