[Chromecast] Set dummy metrics session ID for browser tests

chromecast/base/metrics/cast_metrics_helper.h

Index: chromecast/base/metrics/cast_metrics_helper.h
diff --git a/chromecast/base/metrics/cast_metrics_helper.h b/chromecast/base/metrics/cast_metrics_helper.h
index 5535f73d43fc2100c890cc1721205f2f4b6e55cc..6f3fca2886f6a85274d445034dc20f786c081bfe 100644
--- a/chromecast/base/metrics/cast_metrics_helper.h
+++ b/chromecast/base/metrics/cast_metrics_helper.h
@@ -103,6 +103,9 @@ class CastMetricsHelper {
   // CastMetricsHelper only honors the last one.
   virtual void SetRecordActionCallback(const RecordActionCallback& callback);
 
+  // Sets an all-0's session ID for running browser tests.
+  void SetDummySessionIdForTesting();
+
  protected:
   // Creates a CastMetricsHelper instance with no task runner. This should only
   // be used by tests, since invoking any non-overridden methods on this