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

chrome/common/pref_names.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/common/pref_names.h"
 
 namespace prefs {
 
 // *************** PROFILE PREFS ***************
 // These are attached to the user profile
@@ skipping 511 matching lines @@
 // Boolean controlling whether printing is enabled.
 const char kPrintingEnabled[] = "printing.enabled";
 
 // String pref to define the default values for print overlays.
 const char kPrintingPageHeaderLeft[] = "printing.page.header.left";
 const char kPrintingPageHeaderCenter[] = "printing.page.header.center";
 const char kPrintingPageHeaderRight[] = "printing.page.header.right";
 const char kPrintingPageFooterLeft[] = "printing.page.footer.left";
 const char kPrintingPageFooterCenter[] = "printing.page.footer.center";
 const char kPrintingPageFooterRight[] = "printing.page.footer.right";
+
+// Boolean value that is set to true if print preview has been enabled once for
+// supported platforms.
+#if defined(GOOGLE_CHROME_BUILD) && !defined(OS_MACOSX) && !defined(OS_CHROMEOS)
+const char kPrintingPrintPreviewEnabledOnce[] =
+    "printing.print_preview_enabled_once";
+#endif
+
 #if defined(TOOLKIT_USES_GTK)
 // GTK specific preference on whether we should match the system GTK theme.
 const char kUsesSystemTheme[] = "extensions.theme.use_system";
 #endif
 const char kCurrentThemePackFilename[] = "extensions.theme.pack";
 const char kCurrentThemeID[] = "extensions.theme.id";
 const char kCurrentThemeImages[] = "extensions.theme.images";
 const char kCurrentThemeColors[] = "extensions.theme.colors";
 const char kCurrentThemeTints[] = "extensions.theme.tints";
 const char kCurrentThemeDisplayProperties[] = "extensions.theme.properties";
@@ skipping 828 matching lines @@
 const char kRegisteredProtocolHandlers[] =
   "custom_handlers.registered_protocol_handlers";
 
 // List of protocol handlers the user has requested not to be asked about again.
 const char kIgnoredProtocolHandlers[] =
   "custom_handlers.ignored_protocol_handlers";
 
 // Whether user-specified handlers for protocols and content types can be
 // specified.
 const char kCustomHandlersEnabled[] = "custom_handlers.enabled";
+
 }  // namespace prefs