Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

chrome/test/nacl/nacl_browsertest_uma.cc

 // 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.
 
-#include "chrome/test/base/uma_histogram_helper.h"
+#include "chrome/test/base/chrome_histogram_tester.h"
 #include "chrome/test/nacl/nacl_browsertest_util.h"
 #include "components/nacl/browser/nacl_browser.h"
 #include "native_client/src/trusted/service_runtime/nacl_error_code.h"
 #include "ppapi/c/private/ppb_nacl_private.h"
 
 namespace {
 
 NACL_BROWSER_TEST_F(NaClBrowserTest, SuccessfulLoadUMA, {
+  ChromeHistogramTester histograms;
   // Load a NaCl module to generate UMA data.
   RunLoadTest(FILE_PATH_LITERAL("nacl_load_test.html"));
 
   // Make sure histograms from child processes have been accumulated in the
   // browser brocess.
-  UMAHistogramHelper histograms;
-  histograms.Fetch();
+  histograms.FetchTestingSnapshot();
 
   // Did the plugin report success?
   histograms.ExpectUniqueSample("NaCl.LoadStatus.Plugin",
                                 PP_NACL_ERROR_LOAD_SUCCESS, 1);
 
   // Did the sel_ldr report success?
   histograms.ExpectUniqueSample("NaCl.LoadStatus.SelLdr",
                                 LOAD_OK, 1);
 
   // Check validation cache usage:
@@ skipping 50 matching lines @@
 class NaClBrowserTestVcacheExtension:
       public NaClBrowserTestNewlibExtension {
  public:
   virtual base::FilePath::StringType Variant() OVERRIDE {
     return FILE_PATH_LITERAL("extension_vcache_test/newlib");
   }
 };
 
 IN_PROC_BROWSER_TEST_F(NaClBrowserTestVcacheExtension,
                        ValidationCacheOfMainNexe) {
+  ChromeHistogramTester histograms;
   // Hardcoded extension AppID that corresponds to the hardcoded
   // public key in the manifest.json file. We need to load the extension
   // nexe from the same origin, so we can't just try to load the extension
   // nexe as a mime-type handler from a non-extension URL.
   base::FilePath::StringType full_url =
       FILE_PATH_LITERAL("chrome-extension://cbcdidchbppangcjoddlpdjlenngjldk/")
       FILE_PATH_LITERAL("extension_validation_cache.html");
   RunNaClIntegrationTest(full_url, true);
 
   // Make sure histograms from child processes have been accumulated in the
   // browser brocess.
-  UMAHistogramHelper histograms;
-  histograms.Fetch();
+  histograms.FetchTestingSnapshot();
   // Should have received 2 validation queries (one for IRT and one for NEXE),
   // and responded with a miss.
   histograms.ExpectBucketCount("NaCl.ValidationCache.Query",
                                nacl::NaClBrowser::CACHE_MISS, 2);
   // TOTAL should then be 2 queries so far.
   histograms.ExpectTotalCount("NaCl.ValidationCache.Query", 2);
   // Should have received a cache setting afterwards for IRT and nexe.
   histograms.ExpectBucketCount("NaCl.ValidationCache.Set",
                                nacl::NaClBrowser::CACHE_HIT, 2);
 
   // Load it again to hit the cache.
   RunNaClIntegrationTest(full_url, true);
-  histograms.Fetch();
+  histograms.FetchTestingSnapshot();
   // Should have received 2 more validation queries later (IRT and NEXE),
   // and responded with a hit.
   histograms.ExpectBucketCount("NaCl.ValidationCache.Query",
                                nacl::NaClBrowser::CACHE_HIT, 2);
   // TOTAL should then be 4 queries now.
   histograms.ExpectTotalCount("NaCl.ValidationCache.Query", 4);
   // Still only 2 settings.
   histograms.ExpectTotalCount("NaCl.ValidationCache.Set", 2);
 }
 
 // Test that validation for the 2 PNaCl translator nexes can be cached.
 IN_PROC_BROWSER_TEST_F(NaClBrowserTestPnacl,
                        ValidationCacheOfTranslatorNexes) {
+  ChromeHistogramTester histograms;
   // Run a load test w/ one pexe cache identity.
   RunLoadTest(FILE_PATH_LITERAL("pnacl_options.html?use_nmf=o_0"));
 
-  UMAHistogramHelper histograms;
-  histograms.Fetch();
+  histograms.FetchTestingSnapshot();
   // Should have received 3 validation queries:
   // - One for IRT for actual application
   // - Two for two translator nexes
   // The translators don't currently use the IRT, so there is no IRT cache
   // query for those two loads. The PNaCl main nexe comes from a
   // delete-on-close temp file, so it doesn't have a stable identity
   // for validation caching. All three query results should be misses.
   histograms.ExpectUniqueSample("NaCl.ValidationCache.Query",
                                 nacl::NaClBrowser::CACHE_MISS, 3);
   // Should have received a cache setting afterwards for IRT and translators.
@@ skipping 14 matching lines @@
   // No extra cache settings.
   histograms.ExpectUniqueSample("NaCl.ValidationCache.Set",
                                nacl::NaClBrowser::CACHE_HIT, 3);
 }
 
 
 // TODO(ncbray) convert the rest of nacl_uma.py (currently in the NaCl repo.)
 // Test validation failures and crashes.
 
 }  // namespace