Be explicit about namespace testing to not mix it with blink::testing

third_party/WebKit/Source/platform/scheduler/renderer/task_duration_metric_reporter_unittest.cc

 // Copyright 2017 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 "platform/scheduler/renderer/task_duration_metric_reporter.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/values.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace blink {
 namespace scheduler {
 
 namespace {
 
-using testing::_;
-using testing::Mock;
+using ::testing::_;
+using ::testing::Mock;
 
 class FakeHistogram : public base::HistogramBase {
  public:
   FakeHistogram() : base::HistogramBase("fake") {}
   ~FakeHistogram() override = default;
 
   MOCK_METHOD2(AddCount, void(base::HistogramBase::Sample, int));
   MOCK_CONST_METHOD0(name_hash, uint64_t());
   MOCK_CONST_METHOD0(GetHistogramType, base::HistogramType());
   MOCK_CONST_METHOD3(HasConstructionArguments,
@@ skipping 41 matching lines @@
   Mock::VerifyAndClearExpectations(&histogram);
 
   EXPECT_CALL(histogram, AddCount(2, 16));
   metric_reporter.RecordTask(static_cast<TaskQueue::QueueType>(2),
                              base::TimeDelta::FromMicroseconds(15600));
   Mock::VerifyAndClearExpectations(&histogram);
 }
 
 }  // namespace scheduler
 }  // namespace blink