Return a NULL histogram pointer on construction error

chrome/test/data/extensions/api_test/metrics/test.js

 // Copyright (c) 2012 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.
 
 // metrics api test
 // browser_tests.exe --gtest_filter=ExtensionApiTest.Metrics
 
 // Any changes to the logging done in these functions should be matched
 // with the checks done in IN_PROC_BROWSER_TEST_F(ExtensionApiTest, Metrics).
 // See metrics_apitest.cc.
@@ skipping 74 matching lines @@
 
   function getVariationParams2() {
     chrome.metricsPrivate.getVariationParams(
         'apitestfieldtrial2', function(params) {
       chrome.test.assertEq(undefined, chrome.runtime.lastError);
       chrome.test.assertEq({a: 'aa', b: 'bb'}, params);
       chrome.test.succeed();
     });
   },
 
+  function testBucketSizeChanges() {
+    var linear1 = {
+      'metricName': 'test.bucketchange.linear',
+      'type': 'histogram-linear',
+      'min': 0,
+      'max': 100,
+      'buckets': 10
+    };
+    var linear2 = {
+      'metricName': 'test.bucketchange.linear',
+      'type': 'histogram-linear',
+      'min': 0,
+      'max': 100,
+      'buckets': 20
+    };
+    var log1 = {
+      'metricName': 'test.bucketchange.log',
+      'type': 'histogram-log',
+      'min': 0,
+      'max': 100,
+      'buckets': 10
+    };
+    var log2 = {
+      'metricName': 'test.bucketchange.log',
+      'type': 'histogram-log',
+      'min': 0,
+      'max': 100,
+      'buckets': 20
+    };
+
+    chrome.metricsPrivate.recordValue(linear1, 42);
+    // This one should be rejected because the bucket count is different.
+    // We check for sample count == 2 in metrics_apitest.cc
+    chrome.metricsPrivate.recordValue(linear2, 42);
+    chrome.metricsPrivate.recordValue(linear1, 42);
+
+    chrome.metricsPrivate.recordValue(log1, 42);
+    // This one should be rejected because the bucket count is different.
+    // We check for sample count == 2 in metrics_apitest.cc
+    chrome.metricsPrivate.recordValue(log2, 42);
+    chrome.metricsPrivate.recordValue(log1, 42);
+
+    chrome.test.succeed();
+  },
+
 ]);