Test field trial group with startswith rather than equals.

webrtc/system_wrappers/include/field_trial.h

Index: webrtc/system_wrappers/include/field_trial.h
diff --git a/webrtc/system_wrappers/include/field_trial.h b/webrtc/system_wrappers/include/field_trial.h
index 62fbfd1a50e59dd37c5c712f012af932b7940626..d649191563e9697344748266206ad065bfb49c33 100644
--- a/webrtc/system_wrappers/include/field_trial.h
+++ b/webrtc/system_wrappers/include/field_trial.h
@@ -62,6 +62,10 @@ namespace field_trial {
 // Note: To keep things tidy append all the trial names with WebRTC.
 std::string FindFullName(const std::string& name);
 
+// Convenience method, returns true iff FindFullName(name) return a string that
+// starts with "Enabled".
+bool IsEnabled(const char* name);
+
 }  // namespace field_trial
 }  // namespace webrtc