[Chromecast] Don't log time to first paint if no app has been set.

chromecast/base/metrics/cast_metrics_helper.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chromecast/base/metrics/cast_metrics_helper.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/location.h"
 #include "base/message_loop/message_loop_proxy.h"
@@ skipping 131 matching lines @@
   MAKE_SURE_THREAD(LogMediaPause);
   RecordSimpleAction(EncodeAppInfoIntoMetricsName(
       "MediaPause",
       app_id_,
       session_id_,
       sdk_version_));
 }
 
 void CastMetricsHelper::LogTimeToFirstPaint() {
   MAKE_SURE_THREAD(LogTimeToFirstPaint);
+  if (app_id_.empty())
+    return;
   base::TimeDelta launch_time = base::TimeTicks::Now() - app_start_time_;
   const std::string uma_name(GetMetricsNameWithAppName("Startup",
                                                        "TimeToFirstPaint"));
   LogMediumTimeHistogramEvent(uma_name, launch_time);
   LOG(INFO) << uma_name << " is " << launch_time.InSecondsF() << " seconds.";
 }
 
 void CastMetricsHelper::LogTimeToDisplayVideo() {
   if (!new_startup_time_) {  // For faster check.
     return;
@@ skipping 153 matching lines @@
     const base::TimeDelta& value) {
   // Follow UMA_HISTOGRAM_MEDIUM_TIMES definition.
   LogTimeHistogramEvent(name, value,
                         base::TimeDelta::FromMilliseconds(10),
                         base::TimeDelta::FromMinutes(3),
                         50);
 }
 
 }  // namespace metrics
 }  // namespace chromecast