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

chrome/browser/prerender/prerender_nostate_prefetch_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 "base/command_line.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_split.h"
 #include "base/task_scheduler/post_task.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/history/history_test_utils.h"
 #include "chrome/browser/prerender/prerender_handle.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_manager_factory.h"
 #include "chrome/browser/prerender/prerender_test_utils.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/task_manager/task_manager_browsertest_util.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_commands.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/grit/generated_resources.h"
 #include "chrome/test/base/ui_test_utils.h"
-#include "content/public/common/content_switches.h"
 #include "content/public/common/url_constants.h"
 #include "content/public/test/browser_test_utils.h"
 #include "net/base/escape.h"
 #include "net/dns/mock_host_resolver.h"
 #include "net/test/embedded_test_server/request_handler_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/base/l10n/l10n_util.h"
 
 using prerender::test_utils::CreateCountingInterceptorOnIO;
 using prerender::test_utils::CreatePrefetchOnlyInterceptorOnIO;
@@ skipping 18 matching lines @@
 const char kPrefetchScript[] = "prerender/prefetch.js";
 const char kPrefetchScript2[] = "prerender/prefetch2.js";
 const char kPrefetchSubresourceRedirectPage[] =
     "prerender/prefetch_subresource_redirect.html";
 
 class NoStatePrefetchBrowserTest
     : public test_utils::PrerenderInProcessBrowserTest {
  public:
   NoStatePrefetchBrowserTest() {}
 
-  void SetUpCommandLine(base::CommandLine* command_line) override {
-    PrerenderInProcessBrowserTest::SetUpCommandLine(command_line);
-    command_line->AppendSwitchASCII(
-        switches::kPrerenderMode, switches::kPrerenderModeSwitchValuePrefetch);
+  void SetUpOnMainThread() override {
+    test_utils::PrerenderInProcessBrowserTest::SetUpOnMainThread();
+    PrerenderManager::SetMode(
+        PrerenderManager::PRERENDER_MODE_NOSTATE_PREFETCH);
   }
 
   // Set up a request counter for |path|, which is also the location of the data
   // served by the request.
   void CountRequestFor(const std::string& path_str, RequestCounter* counter) {
     url::StringPieceReplacements<base::FilePath::StringType> replacement;
     base::FilePath file_path = base::FilePath::FromUTF8Unsafe(path_str);
     replacement.SetPathStr(file_path.value());
     const GURL url = src_server()->base_url().ReplaceComponents(replacement);
     CountRequestForUrl(url, path_str, counter);
@@ skipping 416 matching lines @@
 
   // Check that the URL that was prefetched is not in history.
   EXPECT_TRUE(std::find(urls.begin(), urls.end(), prefetched_url) ==
               urls.end());
 
   // The loader URL is the remaining entry.
   EXPECT_EQ(2U, urls.size());
 }
 
 }  // namespace prerender