Add UpdateCurrentAppInfo() interface to record info about current app, including

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 9bacdcbe4b8a00e5c933e2337aed780879f63438..71affde52bc8b39c5ff83a340b49960081220104 100644
--- a/chromecast/base/metrics/cast_metrics_helper.h
+++ b/chromecast/base/metrics/cast_metrics_helper.h
@@ -31,6 +31,16 @@ class CastMetricsHelper {
 
   typedef base::Callback<void(const std::string&)> RecordActionCallback;
 
+  struct MetricsAppInfo {
+    MetricsAppInfo();
+    ~MetricsAppInfo();

[byungchul, 2014/12/11 00:15:26]

Not necessary

[gfhuang, 2014/12/11 02:59:39]

Done.

+
+    std::string action_name;
+    std::string app_id;
+    std::string session_id;
+    std::string sdk_version;
+  };
+
   class MetricsSink {
    public:
     virtual ~MetricsSink() {}
@@ -45,6 +55,14 @@ class CastMetricsHelper {
                              int num_buckets) = 0;
   };
 
+  // Delimiter character used in GetMetricsNameWithAppInfo().
+  static const char kMetricsNameAppInfoDelimiter;

[gunsch, 2014/12/10 22:43:58]

will this be referenced outside this file? I would hope not, if MetricsAppInfo
is being both serialized/deserialized inside the impementation

[gfhuang, 2014/12/11 02:59:39]

Done.

+
+  // Decodes action_name/app_id/session_id/sdk_version from metrics name
+  // generated from GetMetricsNameWithAppInfo().
+  static MetricsAppInfo GetAppInfoFromMetricsName(
+      const std::string& metrics_name);

[byungchul, 2014/12/11 00:15:26]

Do we prefer structure copy? Why not get out param?

and name should be Get(or Extract)MetricsAppInfoFromMetricsName?

[gfhuang, 2014/12/11 02:59:39]

Done.

[byungchul, 2014/12/11 18:35:49]

Though I meant passing the pointer of the structure, I am fine with this either.
Jesse may have a different opinion.

[gfhuang, 2014/12/11 19:20:26]

Ack. define struct has an extra burden to maintain, i think it's ok since only 4
simple fields.

+
   static CastMetricsHelper* GetInstance();
 
   explicit CastMetricsHelper(
@@ -53,6 +71,10 @@ class CastMetricsHelper {
 
   // This function stores the name and startup time of the active application.
   virtual void TagAppStart(const std::string& app_name);
+  // This function updates the info for current active application.
+  virtual void UpdateCurrentAppInfo(const std::string& app_id,
+                                    const std::string& session_id,
+                                    const std::string& sdk_version);
 
   // Logs UMA record for media play/pause user actions.
   virtual void LogMediaPlay();
@@ -81,6 +103,9 @@ class CastMetricsHelper {
   virtual std::string GetMetricsNameWithAppName(
       const std::string& prefix,
       const std::string& suffix) const;
+  // Returns metrics name with app_id/session_id/sdk_version.
+  virtual std::string GetMetricsNameWithAppInfo(
+      const std::string& action_name) const;
 
   // Provides a MetricsSink instance to delegate UMA event logging.
   // Once the delegate interface is set, CastMetricsHelper will not log UMA
@@ -118,6 +143,9 @@ class CastMetricsHelper {
 
   // Currently running app name. Used to construct histogram name.
   std::string app_name_;
+  std::string app_id_;
+  std::string session_id_;
+  std::string sdk_version_;
 
   // Whether a new app start time has been stored but not recorded.
   // After the startup time has been used to generate an UMA event,