Add support for linear/enumeration histograms.

src/platform/metrics/metrics_library.h

Index: src/platform/metrics/metrics_library.h
diff --git a/src/platform/metrics/metrics_library.h b/src/platform/metrics/metrics_library.h
index 5977e724cf1871573e62cb2181204c07c4b2a836..73839605007b39af97c326d924893f33427d2b62 100644
--- a/src/platform/metrics/metrics_library.h
+++ b/src/platform/metrics/metrics_library.h
@@ -33,6 +33,17 @@ class MetricsLibrary {
   static bool SendToChrome(const std::string& name, int sample,
                            int min, int max, int nbuckets);
 
+  // Sends linear histogram data to Chrome for transport to UMA and
+  // returns true on success. This method results in the equivalent of
+  // an asynchronous non-blocking RPC to UMA_HISTOGRAM_ENUMERATION
+  // inside Chrome (see base/histogram.h).
+  //
+  // |sample| is the sample value to be recorded (1 <= |sample| < |max|).
+  // |max| is the maximum value of the histogram samples.
+  // 0 is the implicit underflow bucket.
+  // [|max|,infinity) is the implicit overflow bucket.
+  static bool SendEnumToChrome(const std::string& name, int sample, int max);
+
   // Sends to Autotest and returns true on success.
   static bool SendToAutotest(const std::string& name, int value);
 };