Simplify ExtensionInstallChecker into a single-use class

chrome/browser/extensions/crx_installer_browsertest.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/browser/extensions/crx_installer.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 266 matching lines @@
     ExtensionService* service =
         extensions::ExtensionSystem::Get(browser()->profile())
             ->extension_service();
     scoped_refptr<CrxInstaller> crx_installer(
         CrxInstaller::CreateSilent(service));
     crx_installer->set_error_on_unsupported_requirements(true);
     crx_installer->InstallWebApp(
         CreateWebAppInfo(kAppTitle, kAppDescription, kAppUrl, 64));
     EXPECT_TRUE(WaitForCrxInstallerDone());
     ASSERT_TRUE(crx_installer->extension());
-    ASSERT_FALSE(HasRequirementErrors(crx_installer.get()));
-    ASSERT_FALSE(HasPolicyErrors(crx_installer.get()));
-  }
-
-  bool HasRequirementErrors(CrxInstaller* crx_installer) {
-    return !crx_installer->install_checker_.requirement_errors().empty();
-  }
-
-  bool HasPolicyErrors(CrxInstaller* crx_installer) {
-    return !crx_installer->install_checker_.policy_error().empty();
+    ASSERT_EQ(nullptr, crx_installer->install_checker_.get());

[Devlin, 2017/03/16 19:29:40]

This is testing an implementation detail of the CrxInstaller, rather than
behavior.  If we ever decide to instantiate install_checker_ when there are no
errors, this will fail.  Additionally, this wouldn't catch the case of an
installation being triggered, the install checker running, and finding no
errors.

[michaelpg, 2017/03/17 04:25:22]

This turns out to be the only user of WaitForCrxInstallerDone(), so I've
modified that to ensure the installer finishes *successfully*. So I feel OK
removing this check, which also lets us unfriend CrxInstaller!

   }
 };
 
 class ExtensionCrxInstallerTestWithExperimentalApis
     : public ExtensionCrxInstallerTest {
  protected:
   void SetUpCommandLine(base::CommandLine* command_line) override {
     ExtensionCrxInstallerTest::SetUpCommandLine(command_line);
     command_line->AppendSwitch(switches::kEnableExperimentalExtensionApis);
   }
@@ skipping 414 matching lines @@
     EXPECT_TRUE(WaitForCrxInstallerDone());
     const Extension* extension = installer->extension();
     ASSERT_TRUE(extension);
     ASSERT_EQ(extension_id, extension->id());
     EXPECT_TRUE(ExtensionPrefs::Get(profile())->AllowFileAccess(extension_id));
     EXPECT_TRUE(extension->creation_flags() & Extension::ALLOW_FILE_ACCESS);
   }
 }
 
 }  // namespace extensions