C interface to MediaMetrics

C interface is more stable across upgrades than C++
and simplifies cross-package interfaces in upgradeable components.

Bug: 119675363
Test: parallel metrics generation from nuplayer
Change-Id: I36beeade82a208be64af0860eb6f175a2801b27f
diff --git a/media/libmediametrics/include/MediaAnalyticsItem.h b/media/libmediametrics/include/MediaAnalyticsItem.h
index 263cde7..b99cd91 100644
--- a/media/libmediametrics/include/MediaAnalyticsItem.h
+++ b/media/libmediametrics/include/MediaAnalyticsItem.h
@@ -134,6 +134,7 @@
         bool getRate(Attr, int64_t *count, int64_t *duration, double *rate);
         // Caller owns the returned string
         bool getCString(Attr, char **value);
+        bool getString(Attr, std::string *value);
 
         // parameter indicates whether to close any existing open
         // record with same key before establishing a new record
@@ -176,6 +177,8 @@
 
         std::string toString();
         std::string toString(int version);
+        const char *toCString();
+        const char *toCString(int version);
 
         // are we collecting analytics data
         static bool isEnabled();