Start transition the metrics library to non-static API. Use gmock in tests.

src/platform/metrics/README

Index: src/platform/metrics/README
diff --git a/src/platform/metrics/README b/src/platform/metrics/README
index 912af2713f9583899ed99f32524c8f52473d4497..d8f17c4445fc801774fb9e818c2aa43f4b4a191b 100644
--- a/src/platform/metrics/README
+++ b/src/platform/metrics/README
@@ -32,21 +32,26 @@ a module, you need to do the following:
   $SYSROOT/usr/include/ when the metrics library is built and
   installed.
 
-- Currently, the API includes two static methods:
+- The API includes two methods:
 
-  bool MetricsLibrary::SendToChrome(const std::string& name, int sample,
-                                    int min, int max, int nbuckets)
+  bool MetricsLibrary::SendToUMA(const std::string& name, int sample,
+                                 int min, int max, int nbuckets)
   sends a sample for a regular (exponential) histogram.
 
+  bool MetricsLibrary::SendEnumToUMA(const std::string& name, int sample,
+                                     int max)
+  sends a sample for an enumeration (linear) histogram.
+
+  Currently, the API also includes two deprecated static methods:
+
+  bool MetricsLibrary::SendToChrome(const std::string& name, int sample,
+                                    int min, int max, int nbuckets)
   bool MetricsLibrary::SendEnumToChrome(const std::string& name, int sample,
                                         int max)
-  sends a sample for an enumeration (linear) histogram.
 
-  See API documentation in metrics_library.h under
+  See the API documentation in metrics_library.h under
   src/platform/metrics/.
 
-  TODO: It might be better to convert the API to a dynamic object.
-
 - On the target platform, shortly after the sample is sent it should
   be visible in Chrome through "about:histograms".