[Chromecast] Set dummy metrics session ID for browser tests

chromecast/base/metrics/cast_metrics_helper.cc

Index: chromecast/base/metrics/cast_metrics_helper.cc
diff --git a/chromecast/base/metrics/cast_metrics_helper.cc b/chromecast/base/metrics/cast_metrics_helper.cc
index 9680c8006ed252c19b7e4cfccc6b333c3c3bcfc2..81c3904d2184f5dc547fbf74543282de4754dbda 100644
--- a/chromecast/base/metrics/cast_metrics_helper.cc
+++ b/chromecast/base/metrics/cast_metrics_helper.cc
@@ -91,7 +91,6 @@ CastMetricsHelper* CastMetricsHelper::GetInstance() {
 CastMetricsHelper::CastMetricsHelper(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner)
     : task_runner_(task_runner),
-      session_id_("00000000000000000000000000000000"),
       metrics_sink_(NULL),
       logged_first_audio_(false),
       record_action_callback_(base::Bind(&base::RecordComputedAction)) {
@@ -227,6 +226,11 @@ void CastMetricsHelper::SetRecordActionCallback(
   record_action_callback_ = callback;
 }
 
+void CastMetricsHelper::SetDummySessionIdForTesting() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  session_id_ = "00000000000000000000000000000000";

[gfhuang, 2016/02/13 00:34:01]

use GUID format

"00000000-0000-0000-0000-000000000000"

+}
+
 void CastMetricsHelper::RecordSimpleAction(const std::string& action) {
   MAKE_SURE_THREAD(RecordSimpleAction, action);