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

chrome/renderer/print_web_view_helper_browsertest.cc

Index: chrome/renderer/print_web_view_helper_browsertest.cc
===================================================================
--- chrome/renderer/print_web_view_helper_browsertest.cc	(revision 97007)
+++ chrome/renderer/print_web_view_helper_browsertest.cc	(working copy)
@@ -100,12 +100,6 @@
   virtual ~PrintWebViewHelperTest() {}
 
   virtual void SetUp() {
-    // Append the print preview switch before creating the PrintWebViewHelper.
-#if defined(GOOGLE_CHROME_BUILD) && !defined(OS_CHROMEOS) && !defined(OS_MACOSX)
-    CommandLine::ForCurrentProcess()->AppendSwitch(
-        switches::kDisablePrintPreview);
-#endif
-
     RenderViewTest::SetUp();
   }
 
@@ -301,10 +295,8 @@
 
   virtual void SetUp() {
     // Append the print preview switch before creating the PrintWebViewHelper.
-#if !defined(GOOGLE_CHROME_BUILD) || defined(OS_MACOSX)
     CommandLine::ForCurrentProcess()->AppendSwitch(
         switches::kEnablePrintPreview);
-#endif
 
     RenderViewTest::SetUp();
   }