Add a default implementation in metrics_default.cc of histograms methods in system_wrappers/interface/metrics.h.

Updated tests to use the default implementation and removed the test implementation (webrtc/test/histograms.h).

BUG=

Review-Url: https://codereview.webrtc.org/1915523002
Cr-Commit-Position: refs/heads/master@{#12829}
diff --git a/webrtc/system_wrappers/source/metrics_unittest.cc b/webrtc/system_wrappers/source/metrics_unittest.cc
index 7de6f5e..1d7888f 100644
--- a/webrtc/system_wrappers/source/metrics_unittest.cc
+++ b/webrtc/system_wrappers/source/metrics_unittest.cc
@@ -11,12 +11,11 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 #include "webrtc/system_wrappers/include/metrics.h"
-#include "webrtc/test/histogram.h"
+#include "webrtc/system_wrappers/include/metrics_default.h"
 
 namespace webrtc {
 namespace {
 const int kSample = 22;
-const std::string kName = "Name";
 
 void AddSparseSample(const std::string& name, int sample) {
   RTC_HISTOGRAM_COUNTS_SPARSE_100(name, sample);
@@ -24,92 +23,98 @@
 void AddSampleWithVaryingName(int index, const std::string& name, int sample) {
   RTC_HISTOGRAMS_COUNTS_100(index, name, sample);
 }
-#if GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
+#if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
 void AddSample(const std::string& name, int sample) {
   RTC_HISTOGRAM_COUNTS_100(name, sample);
 }
-#endif  // GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
+#endif  // RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
 }  // namespace
 
-TEST(MetricsTest, InitiallyNoSamples) {
-  test::ClearHistograms();
-  EXPECT_EQ(0, test::NumHistogramSamples(kName));
-  EXPECT_EQ(-1, test::LastHistogramSample(kName));
-}
+class MetricsTest : public ::testing::Test {
+ public:
+  MetricsTest() {}
 
-TEST(MetricsTest, RtcHistogramPercent_AddSample) {
-  test::ClearHistograms();
-  RTC_HISTOGRAM_PERCENTAGE(kName, kSample);
-  EXPECT_EQ(1, test::NumHistogramSamples(kName));
-  EXPECT_EQ(kSample, test::LastHistogramSample(kName));
-}
-
-TEST(MetricsTest, RtcHistogramEnumeration_AddSample) {
-  test::ClearHistograms();
-  RTC_HISTOGRAM_ENUMERATION(kName, kSample, kSample + 1);
-  EXPECT_EQ(1, test::NumHistogramSamples(kName));
-  EXPECT_EQ(kSample, test::LastHistogramSample(kName));
-}
-
-TEST(MetricsTest, RtcHistogramCountsSparse_AddSample) {
-  test::ClearHistograms();
-  RTC_HISTOGRAM_COUNTS_SPARSE_100(kName, kSample);
-  EXPECT_EQ(1, test::NumHistogramSamples(kName));
-  EXPECT_EQ(kSample, test::LastHistogramSample(kName));
-}
-
-TEST(MetricsTest, RtcHistogramCounts_AddSample) {
-  test::ClearHistograms();
-  RTC_HISTOGRAM_COUNTS_100(kName, kSample);
-  EXPECT_EQ(1, test::NumHistogramSamples(kName));
-  EXPECT_EQ(kSample, test::LastHistogramSample(kName));
-}
-
-TEST(MetricsTest, RtcHistogramCounts_AddMultipleSamples) {
-  test::ClearHistograms();
-  const int kNumSamples = 10;
-  for (int i = 0; i < kNumSamples; ++i) {
-    RTC_HISTOGRAM_COUNTS_100(kName, i);
+ protected:
+  virtual void SetUp() {
+    metrics::Reset();
   }
-  EXPECT_EQ(kNumSamples, test::NumHistogramSamples(kName));
-  EXPECT_EQ(kNumSamples - 1, test::LastHistogramSample(kName));
+};
+
+TEST_F(MetricsTest, InitiallyNoSamples) {
+  EXPECT_EQ(0, metrics::NumSamples("NonExisting"));
+  EXPECT_EQ(0, metrics::NumEvents("NonExisting", kSample));
 }
 
-TEST(MetricsTest, RtcHistogramsCounts_AddSample) {
-  test::ClearHistograms();
+TEST_F(MetricsTest, RtcHistogramPercent_AddSample) {
+  const std::string kName = "Percentage";
+  RTC_HISTOGRAM_PERCENTAGE(kName, kSample);
+  EXPECT_EQ(1, metrics::NumSamples(kName));
+  EXPECT_EQ(1, metrics::NumEvents(kName, kSample));
+}
+
+TEST_F(MetricsTest, RtcHistogramEnumeration_AddSample) {
+  const std::string kName = "Enumeration";
+  RTC_HISTOGRAM_ENUMERATION(kName, kSample, kSample + 1);
+  EXPECT_EQ(1, metrics::NumSamples(kName));
+  EXPECT_EQ(1, metrics::NumEvents(kName, kSample));
+}
+
+TEST_F(MetricsTest, RtcHistogramCountsSparse_AddSample) {
+  const std::string kName = "CountsSparse100";
+  RTC_HISTOGRAM_COUNTS_SPARSE_100(kName, kSample);
+  EXPECT_EQ(1, metrics::NumSamples(kName));
+  EXPECT_EQ(1, metrics::NumEvents(kName, kSample));
+}
+
+TEST_F(MetricsTest, RtcHistogramCounts_AddSample) {
+  const std::string kName = "Counts100";
+  RTC_HISTOGRAM_COUNTS_100(kName, kSample);
+  EXPECT_EQ(1, metrics::NumSamples(kName));
+  EXPECT_EQ(1, metrics::NumEvents(kName, kSample));
+}
+
+TEST_F(MetricsTest, RtcHistogramCounts_AddMultipleSamples) {
+  const std::string kName = "Counts200";
+  const int kNumSamples = 10;
+  for (int i = 1; i <= kNumSamples; ++i) {
+    RTC_HISTOGRAM_COUNTS_200(kName, i);
+    EXPECT_EQ(1, metrics::NumEvents(kName, i));
+    EXPECT_EQ(i, metrics::NumSamples(kName));
+  }
+}
+
+TEST_F(MetricsTest, RtcHistogramsCounts_AddSample) {
   AddSampleWithVaryingName(0, "Name1", kSample);
   AddSampleWithVaryingName(1, "Name2", kSample + 1);
   AddSampleWithVaryingName(2, "Name3", kSample + 2);
-  EXPECT_EQ(1, test::NumHistogramSamples("Name1"));
-  EXPECT_EQ(1, test::NumHistogramSamples("Name2"));
-  EXPECT_EQ(1, test::NumHistogramSamples("Name3"));
-  EXPECT_EQ(kSample + 0, test::LastHistogramSample("Name1"));
-  EXPECT_EQ(kSample + 1, test::LastHistogramSample("Name2"));
-  EXPECT_EQ(kSample + 2, test::LastHistogramSample("Name3"));
+  EXPECT_EQ(1, metrics::NumSamples("Name1"));
+  EXPECT_EQ(1, metrics::NumSamples("Name2"));
+  EXPECT_EQ(1, metrics::NumSamples("Name3"));
+  EXPECT_EQ(1, metrics::NumEvents("Name1", kSample + 0));
+  EXPECT_EQ(1, metrics::NumEvents("Name2", kSample + 1));
+  EXPECT_EQ(1, metrics::NumEvents("Name3", kSample + 2));
 }
 
 #if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
-TEST(MetricsTest, RtcHistogramsCounts_InvalidIndex) {
-  EXPECT_DEATH(RTC_HISTOGRAMS_COUNTS_1000(-1, kName, kSample), "");
-  EXPECT_DEATH(RTC_HISTOGRAMS_COUNTS_1000(3, kName, kSample), "");
-  EXPECT_DEATH(RTC_HISTOGRAMS_COUNTS_1000(3u, kName, kSample), "");
+TEST_F(MetricsTest, RtcHistogramsCounts_InvalidIndex) {
+  EXPECT_DEATH(RTC_HISTOGRAMS_COUNTS_1000(-1, "Name", kSample), "");
+  EXPECT_DEATH(RTC_HISTOGRAMS_COUNTS_1000(3, "Name", kSample), "");
+  EXPECT_DEATH(RTC_HISTOGRAMS_COUNTS_1000(3u, "Name", kSample), "");
 }
 #endif
 
-TEST(MetricsTest, RtcHistogramSparse_NonConstantNameWorks) {
-  test::ClearHistograms();
-  AddSparseSample("Name1", kSample);
-  AddSparseSample("Name2", kSample);
-  EXPECT_EQ(1, test::NumHistogramSamples("Name1"));
-  EXPECT_EQ(1, test::NumHistogramSamples("Name2"));
+TEST_F(MetricsTest, RtcHistogramSparse_NonConstantNameWorks) {
+  AddSparseSample("Sparse1", kSample);
+  AddSparseSample("Sparse2", kSample);
+  EXPECT_EQ(1, metrics::NumSamples("Sparse1"));
+  EXPECT_EQ(1, metrics::NumSamples("Sparse2"));
 }
 
-#if GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
-TEST(MetricsTest, RtcHistogram_FailsForNonConstantName) {
-  test::ClearHistograms();
-  AddSample("Name1", kSample);
-  EXPECT_DEATH(AddSample("Name2", kSample), "");
+#if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
+TEST_F(MetricsTest, RtcHistogram_FailsForNonConstantName) {
+  AddSample("ConstantName1", kSample);
+  EXPECT_DEATH(AddSample("NotConstantName1", kSample), "");
 }
-#endif  // GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
+#endif
 
 }  // namespace webrtc