Fix HistogramTester::GetAllSamples when empty.

base/test/histogram_tester_unittest.cc

 // Copyright 2014 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 "base/test/histogram_tester.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/histogram_samples.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 using ::testing::ElementsAre;
+using ::testing::IsEmpty;
 
 static const char kHistogram1[] = "Test1";
 static const char kHistogram2[] = "Test2";
 static const char kHistogram3[] = "Test3";
 static const char kHistogram4[] = "Test4";
 static const char kHistogram5[] = "Test5";
 
 typedef testing::Test HistogramTesterTest;
 
 TEST_F(HistogramTesterTest, Scope) {
@@ skipping 73 matching lines @@
   HistogramTester tester;
   UMA_HISTOGRAM_ENUMERATION(kHistogram5, 2, 5);
   UMA_HISTOGRAM_ENUMERATION(kHistogram5, 3, 5);
   UMA_HISTOGRAM_ENUMERATION(kHistogram5, 3, 5);
   UMA_HISTOGRAM_ENUMERATION(kHistogram5, 5, 5);
 
   EXPECT_THAT(tester.GetAllSamples(kHistogram5),
               ElementsAre(Bucket(2, 1), Bucket(3, 2), Bucket(5, 1)));
 }
 
+TEST_F(HistogramTesterTest, TestGetAllSamples_NoSamples) {
+  HistogramTester tester;
+  EXPECT_THAT(tester.GetAllSamples(kHistogram5), IsEmpty());
+}
+
 }  // namespace base