metrics: Add SendUserActionToUMA() to MetricsLibraryMock.

The metrics daemon doesn't support sending user actions, but
I need this exposed through the mock library so I can use
SendUserActionToUMA() in the power manager.

Change-Id: Ie9e3995df9978768477fe46dcb9ebec4d1fff1d5

BUG=chromium-os:10696
TEST=built for x86-mario with FEATURES=test; checked that the power manager can now use SendUserActionToUMA()

Review URL: http://codereview.chromium.org/6130003

metrics/metrics_library.h

@@ -16,6 +16,7 @@ class MetricsLibraryInterface {
   virtual bool SendToUMA(const std::string& name, int sample,
                          int min, int max, int nbuckets) = 0;
   virtual bool SendEnumToUMA(const std::string& name, int sample, int max) = 0;
+  virtual bool SendUserActionToUMA(const std::string& action) = 0;
   virtual ~MetricsLibraryInterface() {}
 };
 

metrics/metrics_library_mock.h

@@ -18,6 +18,7 @@ class MetricsLibraryMock : public MetricsLibraryInterface {
                                int min, int max, int nbuckets));
   MOCK_METHOD3(SendEnumToUMA, bool(const std::string& name, int sample,
                                    int max));
+  MOCK_METHOD1(SendUserActionToUMA, bool(const std::string& action));
 };
 
 #endif  // METRICS_LIBRARY_MOCK_H_