[Prerender] Get the prerender mode from Finch field trial.

chrome/browser/apps/app_url_redirector_browsertest.cc

 // Copyright 2013 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 "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/windows_version.h"
 #include "build/build_config.h"
 #include "chrome/browser/apps/app_browsertest_util.h"
 #include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/ui/browser_navigator_params.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "content/public/test/browser_test_base.h"
 #include "content/public/test/browser_test_utils.h"
 #include "extensions/test/extension_test_message_listener.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"
 #include "ui/base/page_transition_types.h"
 
 namespace extensions {
 
 class PlatformAppUrlRedirectorBrowserTest : public PlatformAppBrowserTest {
  public:
   void SetUpCommandLine(base::CommandLine* command_line) override;
+  void SetUpOnMainThread() override;
 
  protected:
   // Performs the following sequence:
   // - installs the app |handler| (a relative path under the platform_apps
   // subdirectory);
   // - navigates the current tab to the HTML page |lancher_page| (ditto);
   // - then waits for |handler| to launch and send back a |handler_ack_message|;
   // - finally checks that the resulting app window count is as expected.
   // The |launcher_page| is supposed to trigger a navigation matching one of the
   // url_handlers in the |handler|'s manifest, and thereby launch the |handler|.
@@ skipping 75 matching lines @@
   void TestMismatchingNavigationInBrowser(const char* mismatching_target_page,
                                           ui::PageTransition transition,
                                           const char* success_tab_title,
                                           const char* handler);
 };
 
 void PlatformAppUrlRedirectorBrowserTest::SetUpCommandLine(
     base::CommandLine* command_line) {
   PlatformAppBrowserTest::SetUpCommandLine(command_line);
   command_line->AppendSwitch(::switches::kDisablePopupBlocking);
-  command_line->AppendSwitchASCII(::switches::kPrerenderMode,
-                                  ::switches::kPrerenderModeSwitchValueEnabled);
+}
+
+void PlatformAppUrlRedirectorBrowserTest::SetUpOnMainThread() {
+  PlatformAppBrowserTest::SetUpOnMainThread();
+  prerender::PrerenderManager::SetMode(
+      prerender::PrerenderManager::PRERENDER_MODE_ENABLED);
 }
 
 // TODO(sergeygs): Factor out common functionality from TestXyz,
 // TestNegativeXyz, and TestMismatchingXyz versions.
 
 // TODO(sergeys): Return testing::AssertionErrors from these methods to
 // preserve line numbers and (if applicable) failure messages.
 
 void PlatformAppUrlRedirectorBrowserTest::TestNavigationInTab(
     const char* launcher_page,
@@ skipping 368 matching lines @@
 #if defined (OS_WIN)
   if (base::win::GetVersion() < base::win::VERSION_VISTA) return;  // Bug 301638
 #endif
   TestNavigationInTab(
       "url_handlers/launching_pages/prerender_link.html",
       "url_handlers/handlers/simple",
       "Handler launched");
 }
 
 }  // namespace extensions