Convert ExceptionProcessorTest to use HistogramTester.

Previously, it was querying the StatisticsRecorder
directly, which is not recommended. Use the HistogramTester
helper class which is exactly for this purpose.

Bug: None
Change-Id: I820716f31a96c31540cea14576db616361c63f96
Reviewed-on: https://chromium-review.googlesource.com/894489Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533049}

chrome/browser/mac/exception_processor_unittest.mm

@@ -9,16 +9,10 @@
 #include <sys/wait.h>
 
 #include "base/mac/os_crash_dumps.h"
-#include "base/metrics/histogram_macros.h"
-#include "base/metrics/histogram_samples.h"
-#include "base/metrics/statistics_recorder.h"
+#include "base/test/histogram_tester.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-using base::HistogramBase;
-using base::HistogramSamples;
-using base::StatisticsRecorder;
-
 namespace chrome {
 
 // Generate an NSException with the given name.
@@ -48,9 +42,7 @@ TEST(ExceptionProcessorTest, ExceptionBinning) {
 }
 
 TEST(ExceptionProcessorTest, RecordException) {
-  EXPECT_THAT(StatisticsRecorder::WithName(StatisticsRecorder::GetHistograms(),
-                                           "OSX.NSException"),
-              testing::IsEmpty());
+  base::HistogramTester tester;
 
   // Record some known exceptions.
   RecordExceptionWithUma(ExceptionNamed(NSGenericException));
@@ -71,23 +63,14 @@ TEST(ExceptionProcessorTest, RecordException) {
   RecordExceptionWithUma(nil);
 
   // We should have exactly the right number of exceptions.
-  const StatisticsRecorder::Histograms histograms =
-      StatisticsRecorder::WithName(StatisticsRecorder::GetHistograms(),
-                                   "OSX.NSException");
-  ASSERT_THAT(histograms, testing::SizeIs(1));
-  EXPECT_EQ(HistogramBase::kUmaTargetedHistogramFlag, histograms[0]->flags());
-
-  std::unique_ptr<HistogramSamples> samples(histograms[0]->SnapshotSamples());
-  EXPECT_EQ(4, samples->GetCount(0));
-  EXPECT_EQ(1, samples->GetCount(1));
-  EXPECT_EQ(3, samples->GetCount(2));
-  EXPECT_EQ(2, samples->GetCount(3));
+  const char kHistogramName[] = "OSX.NSException";
+  tester.ExpectBucketCount(kHistogramName, 0, 4);
+  tester.ExpectBucketCount(kHistogramName, 1, 1);
+  tester.ExpectBucketCount(kHistogramName, 2, 3);
+  tester.ExpectBucketCount(kHistogramName, 3, 2);
 
   // The unknown exceptions should end up in the overflow bucket.
-  EXPECT_TRUE(histograms[0]->HasConstructionArguments(1,
-                                                      kUnknownNSException,
-                                                      kUnknownNSException + 1));
-  EXPECT_EQ(4, samples->GetCount(kUnknownNSException));
+  tester.ExpectBucketCount(kHistogramName, kUnknownNSException, 4);
 }
 
 void RaiseExceptionInRunLoop() {