Add Skia support for UMA stats

This is the counterpart to crrev.com/1652053004

This adds a simple wrapper around the UMA_HISTOGRAM_* macros
for inclusion in SkUserConfig. Along with the corresponding
Skia change, this allows Skia to log stats which will be
picked up by the UMA system.

BUG=

Review URL: https://codereview.chromium.org/1659303002

Cr-Commit-Position: refs/heads/master@{#373933}

5 files changed, 87 insertions, 0 deletions

diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index af09b70..2e64ee8 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -297,6 +297,7 @@ component("skia") {
     "ext/platform_device_mac.cc",
     "ext/platform_device_win.cc",
     "ext/recursive_gaussian_convolution.cc",
+    "ext/skia_histogram.cc",
     "ext/skia_memory_dump_provider.cc",
     "ext/skia_trace_memory_dump_impl.cc",
     "ext/skia_utils_base.cc",
diff --git a/skia/config/SkUserConfig.h b/skia/config/SkUserConfig.h
index 4b547a9..f6b4bea 100644
--- a/skia/config/SkUserConfig.h
+++ b/skia/config/SkUserConfig.h
@@ -17,6 +17,8 @@
 #ifndef SkUserConfig_DEFINED
 #define SkUserConfig_DEFINED
 
+#include "skia/ext/skia_histogram.h"
+
 /*  SkTypes.h, the root of the public header files, does the following trick:
 
     #include <SkPreConfig.h>
diff --git a/skia/ext/skia_histogram.cc b/skia/ext/skia_histogram.cc
new file mode 100644
index 0000000..430e66b
--- /dev/null
+++ b/skia/ext/skia_histogram.cc
@@ -0,0 +1,43 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "skia/ext/skia_histogram.h"
+
+#include <type_traits>
+#include "base/metrics/histogram.h"
+
+// In order to prevent Chrome headers from leaking into Skia, we use a raw
+// intptr_t in the header, rather than the base::subtle::AtomicWord. Make sure
+// this is a valid assumption.
+static_assert(std::is_same<intptr_t, base::subtle::AtomicWord>::value,
+              "To allow for header decoupling, skia_histogram.h uses intptr_t "
+              "instead of a base::subtle::AtomicWord. These must be the same "
+              "type");
+
+namespace skia {
+
+// Wrapper around HISTOGRAM_POINTER_USE - mimics UMA_HISTOGRAM_BOOLEAN but
+// allows for an external atomic_histogram_pointer.
+void HistogramBoolean(intptr_t* atomic_histogram_pointer,
+                      const char* name,
+                      bool sample) {
+  HISTOGRAM_POINTER_USE(
+      atomic_histogram_pointer, name, AddBoolean(sample),
+      base::BooleanHistogram::FactoryGet(
+          name, base::HistogramBase::kUmaTargetedHistogramFlag));
+}
+
+// Wrapper around HISTOGRAM_POINTER_USE - mimics UMA_HISTOGRAM_ENUMERATION but
+// allows for an external atomic_histogram_pointer.
+void HistogramEnumeration(intptr_t* atomic_histogram_pointer,
+                          const char* name,
+                          int sample,
+                          int boundary_value) {
+  HISTOGRAM_POINTER_USE(atomic_histogram_pointer, name, Add(sample),
+                        base::LinearHistogram::FactoryGet(
+                            name, 1, boundary_value, boundary_value + 1,
+                            base::HistogramBase::kUmaTargetedHistogramFlag));
+}
+
+}  // namespace skia
diff --git a/skia/ext/skia_histogram.h b/skia/ext/skia_histogram.h
new file mode 100644
index 0000000..0a2c7f2
--- /dev/null
+++ b/skia/ext/skia_histogram.h
@@ -0,0 +1,40 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SKIA_EXT_SKIA_HISTOGRAM_H_
+#define SKIA_EXT_SKIA_HISTOGRAM_H_
+
+#include <cstdint>
+
+// This file exposes Chrome's histogram functionality to Skia, without bringing
+// in any Chrome specific headers. To achieve the same level of optimization as
+// is present in Chrome, we need to use an inlined atomic pointer. This macro
+// defines a placeholder atomic which will be inlined into the call-site. This
+// placeholder is passed to the actual histogram logic in Chrome.
+#define SK_HISTOGRAM_POINTER_HELPER(function, ...)    \
+  do {                                                \
+    static intptr_t atomic_histogram_pointer = 0;     \
+    function(&atomic_histogram_pointer, __VA_ARGS__); \
+  } while (0)
+
+#define SK_HISTOGRAM_BOOLEAN(name, sample) \
+  SK_HISTOGRAM_POINTER_HELPER(skia::HistogramBoolean, "Skia." name, sample)
+
+#define SK_HISTOGRAM_ENUMERATION(name, sample, boundary_value)          \
+  SK_HISTOGRAM_POINTER_HELPER(skia::HistogramEnumeration, "Skia." name, \
+                              sample, boundary_value)
+
+namespace skia {
+
+void HistogramBoolean(intptr_t* atomic_histogram_pointer,
+                      const char* name,
+                      bool sample);
+void HistogramEnumeration(intptr_t* atomic_histogram_pointer,
+                          const char* name,
+                          int sample,
+                          int boundary_value);
+
+}  // namespace skia
+
+#endif  // SKIA_EXT_SKIA_HISTOGRAM_H_
diff --git a/skia/skia_chrome.gypi b/skia/skia_chrome.gypi
index 4927624..8d4f850 100644
--- a/skia/skia_chrome.gypi
+++ b/skia/skia_chrome.gypi
@@ -47,6 +47,7 @@
     'ext/recursive_gaussian_convolution.cc',
     'ext/SkDiscardableMemory_chrome.cc',
     'ext/SkMemory_new_handler.cpp',
+    'ext/skia_histogram.cc',
     'ext/skia_memory_dump_provider.cc',
     'ext/skia_trace_memory_dump_impl.cc',
     'ext/skia_utils_base.cc',