Print Preview: Add "print preview" back to about:flags; enable it by default just once.

chrome/browser/browser_main.cc

 // Copyright (c) 2011 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/browser_main.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 1407 matching lines @@
         (parsed_command_line.HasSwitch(switches::kApp) ||
          parsed_command_line.HasSwitch(switches::kAppId) ||
          parsed_command_line.HasSwitch(switches::kNoFirstRun)))
       first_run_ui_bypass = true;
   }
 
   // TODO(viettrungluu): why don't we run this earlier?
   if (!parsed_command_line.HasSwitch(switches::kNoErrorDialogs))
     WarnAboutMinimumSystemRequirements();
 
+  // Enable print preview once for supported platforms.
+#if defined(GOOGLE_CHROME_BUILD) && !defined(OS_MACOSX) && !defined(OS_CHROMEOS)
+  local_state->RegisterBooleanPref(prefs::kPrintingPrintPreviewEnabledOnce,
+                                   false,
+                                   PrefService::UNSYNCABLE_PREF);
+  if (!local_state->GetBoolean(prefs::kPrintingPrintPreviewEnabledOnce)) {
+    local_state->SetBoolean(prefs::kPrintingPrintPreviewEnabledOnce, true);
+    about_flags::SetExperimentEnabled(local_state, "print-preview", true);
+  }
+#endif
+
   // Convert active labs into switches. Modifies the current command line.
   about_flags::ConvertFlagsToSwitches(local_state,
                                       CommandLine::ForCurrentProcess());
 
   InitializeNetworkOptions(parsed_command_line);
   InitializeURLRequestThrottlerManager(browser_process->net_log());
 
   // Initialize histogram synchronizer system. This is a singleton and is used
   // for posting tasks via NewRunnableMethod. Its deleted when it goes out of
   // scope. Even though NewRunnableMethod does AddRef and Release, the object
@@ skipping 557 matching lines @@
 #if defined(OS_CHROMEOS)
   // To be precise, logout (browser shutdown) is not yet done, but the
   // remaining work is negligible, hence we say LogoutDone here.
   chromeos::BootTimesLoader::Get()->AddLogoutTimeMarker("LogoutDone",
                                                         false);
   chromeos::BootTimesLoader::Get()->WriteLogoutTimes();
 #endif
   TRACE_EVENT_END_ETW("BrowserMain", 0, 0);
   return result_code;
 }