Don't log error from metricsPrivate API when GetVariationParams fails to find a

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 72 matching lines @@
       chrome.test.assertEq('group1', group);
       chrome.test.succeed();
     };
 
     chrome.metricsPrivate.getFieldTrial('apitestfieldtrial1', test1Callback);
   },
 
   function getVariationParams1() {
     chrome.metricsPrivate.getVariationParams(
         'apitestfieldtrial1', function(params) {
-      chrome.test.assertEq('Variation parameters are unavailable.',
-                           chrome.runtime.lastError.message);
+      chrome.test.assertEq(undefined, chrome.runtime.lastError);

[not at google - send to devlin, 2014/05/07 15:04:04]

Now's use of this function and the test disagree.

       chrome.test.assertEq(undefined, params);
       chrome.test.succeed();
     });
   },
 
   function getVariationParams2() {
     chrome.metricsPrivate.getVariationParams(
         'apitestfieldtrial2', function(params) {
       chrome.test.assertEq(undefined, chrome.runtime.lastError);
       chrome.test.assertEq({a: 'aa', b: 'bb'}, params);
@@ skipping 41 matching lines @@
     // 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();
   },
 
 ]);