Fix ios_chrome_unittests to crash on DCHECK failure.

ios/chrome/test/ios_chrome_unit_test_suite.mm

 // Copyright 2015 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 "ios/chrome/test/ios_chrome_unit_test_suite.h"
 
 #include "base/macros.h"
+#include "base/metrics/user_metrics.h"
 #include "base/path_service.h"
+#include "base/test/test_simple_task_runner.h"
 #include "components/content_settings/core/common/content_settings_pattern.h"
 #include "ios/chrome/browser/browser_state/browser_state_keyed_service_factories.h"
 #include "ios/chrome/browser/chrome_paths.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
 #include "ios/chrome/test/testing_application_context.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #include "ios/public/provider/chrome/browser/test_chrome_provider_initializer.h"
 #include "ios/web/public/web_client.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 29 matching lines @@
   std::unique_ptr<ios::TestChromeProviderInitializer>
       test_ios_chrome_provider_initializer_;
   std::unique_ptr<ApplicationContext> application_context_;
 
   DISALLOW_COPY_AND_ASSIGN(IOSChromeUnitTestSuiteInitializer);
 };
 
 }  // namespace
 
 IOSChromeUnitTestSuite::IOSChromeUnitTestSuite(int argc, char** argv)
-    : web::WebTestSuite(argc, argv) {}
+    : web::WebTestSuite(argc, argv),
+      action_task_runner_(new base::TestSimpleTaskRunner) {}
 
 IOSChromeUnitTestSuite::~IOSChromeUnitTestSuite() {}
 
 void IOSChromeUnitTestSuite::Initialize() {
   // Add an additional listener to do the extra initialization for unit tests.
   // It will be started before the base class listeners and ended after the
   // base class listeners.
   testing::TestEventListeners& listeners =
       testing::UnitTest::GetInstance()->listeners();
   listeners.Append(new IOSChromeUnitTestSuiteInitializer);
 
   // Call the superclass Initialize() method after adding the listener.
   web::WebTestSuite::Initialize();
 
   // Ensure that all BrowserStateKeyedServiceFactories are built before any
   // test is run so that the dependencies are correctly resolved.
   EnsureBrowserStateKeyedServiceFactoriesBuilt();
 
+  // Register a SingleThreadTaskRunner for base::RecordAction as overridding
+  // it in individual tests is unsafe (as there is no way to unregister).
+  base::SetRecordActionTaskRunner(action_task_runner_);
+
   ios::RegisterPathProvider();
   ui::RegisterPathProvider();
   url::AddStandardScheme(kChromeUIScheme, url::SCHEME_WITHOUT_PORT);
   ContentSettingsPattern::SetNonWildcardDomainNonPortScheme(
       kDummyExtensionScheme);
 }