Add Histogram Macros to Skia

include/core/SkHistogramLogging.h

+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkHistogramLogging_DEFINED
+#define SkHistogramLogging_DEFINED
+
+#ifdef SK_HISTOGRAM_LOGGING_CUSTOM_SETUP_HEADER
+  // This header file, if present, should define alternative implementations of
+  // the macros defined in the #else block.
+  #include SK_HISTOGRAM_LOGGING_CUSTOM_SETUP_HEADER
+#else
+  // Macro used to track a boolean event. Value must be either true or false.
+  #define SK_HISTOGRAM_BOOLEAN(name, value)
+
+  // Macro used to track the frequency of certain values of an enumeration. All
+  // values must be less than |boundary_value| and |boundary_value| must not
+  // change over multiple calls.
+  #define SK_HISTOGRAM_ENUMERATION(name, value, boundary_value)
+#endif
+
+#endif