Simplify BrowserContext by removing redundant methods.

extensions/browser/api_unittest.cc

 // Copyright 2014 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 "extensions/browser/api_unittest.h"
 
 #include "base/values.h"
 #include "components/user_prefs/user_prefs.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
@@ skipping 35 matching lines @@
 
   extension_ = ExtensionBuilder()
                    .SetManifest(DictionaryBuilder()
                                     .Set("name", "Test")
                                     .Set("version", "1.0")
                                     .Build())
                    .SetLocation(Manifest::UNPACKED)
                    .Build();
 }
 
+void ApiUnitTest::TearDown() {
+  extension_ = nullptr;
+  contents_.reset();
+  ExtensionsTest::TearDown();
+}
+
 void ApiUnitTest::CreateBackgroundPage() {
   if (!contents_) {
     GURL url = BackgroundInfo::GetBackgroundURL(extension());
     if (url.is_empty())
       url = GURL(url::kAboutBlankURL);
     contents_.reset(
         content::WebContents::Create(content::WebContents::CreateParams(
             browser_context(),
             content::SiteInstance::CreateForURL(browser_context(), url))));
   }
@@ skipping 47 matching lines @@
     function->SetRenderFrameHost(contents_->GetMainFrame());
   return utils::RunFunctionAndReturnError(function, args, browser_context());
 }
 
 void ApiUnitTest::RunFunction(UIThreadExtensionFunction* function,
                               const std::string& args) {
   RunFunctionAndReturnValue(function, args);
 }
 
 }  // namespace extensions