Add a default implementation in metrics_default.cc of histograms methods in system_wrappers/interfac

webrtc/video/send_delay_stats_unittest.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/video/send_delay_stats.h"
 
 #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 uint32_t kSsrc1 = 17;
 const uint32_t kSsrc2 = 42;
 const uint32_t kRtxSsrc1 = 18;
 const uint32_t kRtxSsrc2 = 43;
 const uint16_t kPacketId = 2345;
 const int64_t kMaxPacketDelayMs = 11000;
 const int kMinRequiredSamples = 200;
@@ skipping 69 matching lines @@
   clock_.AdvanceTimeMilliseconds(kMaxPacketDelayMs);  // 0xffff, 0 -> old.
   OnSendPacket(2u, kSsrc1, kCaptureTimeMs + 2);
 
   EXPECT_FALSE(OnSentPacket(0xffffu));  // Old removed.
   EXPECT_FALSE(OnSentPacket(0u));       // Old removed.
   EXPECT_TRUE(OnSentPacket(1u));
   EXPECT_TRUE(OnSentPacket(2u));
 }
 
 TEST_F(SendDelayStatsTest, HistogramsAreUpdated) {
-  test::ClearHistograms();
+  metrics::Reset();
   const int64_t kDelayMs1 = 5;
   const int64_t kDelayMs2 = 10;
   uint16_t id = 0;
   for (int i = 0; i < kMinRequiredSamples; ++i) {
     OnSendPacket(++id, kSsrc1);
     clock_.AdvanceTimeMilliseconds(kDelayMs1);
     EXPECT_TRUE(OnSentPacket(id));
     OnSendPacket(++id, kSsrc2);
     clock_.AdvanceTimeMilliseconds(kDelayMs2);
     EXPECT_TRUE(OnSentPacket(id));
   }
   stats_.reset();
-  EXPECT_EQ(2, test::NumHistogramSamples("WebRTC.Video.SendDelayInMs"));
-  EXPECT_EQ(kDelayMs2, test::LastHistogramSample("WebRTC.Video.SendDelayInMs"));
+  EXPECT_EQ(2, metrics::NumSamples("WebRTC.Video.SendDelayInMs"));
+  EXPECT_EQ(1, metrics::NumEvents("WebRTC.Video.SendDelayInMs", kDelayMs1));
+  EXPECT_EQ(1, metrics::NumEvents("WebRTC.Video.SendDelayInMs", kDelayMs2));
 }
 
 }  // namespace webrtc