Add RAIL tracing category to Chrome tracing.

cc/debug/benchmark_instrumentation.cc

Index: cc/debug/benchmark_instrumentation.cc
diff --git a/cc/debug/benchmark_instrumentation.cc b/cc/debug/benchmark_instrumentation.cc
index c32565ee62230ccc2d71e6d5972337da3ff13012..ff2217154f43b24261196cbe4db94419f7b52761 100644
--- a/cc/debug/benchmark_instrumentation.cc
+++ b/cc/debug/benchmark_instrumentation.cc
@@ -13,10 +13,9 @@ namespace benchmark_instrumentation {
 // The benchmarks search for events and their arguments by name.
 
 void IssueImplThreadRenderingStatsEvent(const RenderingStats& stats) {
-  TRACE_EVENT_INSTANT1("benchmark",
-                       "BenchmarkInstrumentation::ImplThreadRenderingStats",
-                       TRACE_EVENT_SCOPE_THREAD,
-                       "data", stats.AsTraceableData());
+  TRACE_EVENT_INSTANT1(
+      "benchmark,rail", "BenchmarkInstrumentation::ImplThreadRenderingStats",
+      TRACE_EVENT_SCOPE_THREAD, "data", stats.AsTraceableData());
 }
 
 void IssueDisplayRenderingStatsEvent() {