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

chrome/browser/ui/webui/print_preview_ui_unittest.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 "base/command_line.h"
 #include "base/memory/ref_counted_memory.h"
 #include "chrome/browser/printing/print_preview_tab_controller.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/webui/print_preview_ui.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/browser_with_test_window_test.h"
 #include "chrome/test/testing_profile.h"
 #include "content/browser/tab_contents/tab_contents.h"
 
 namespace {
 
 const unsigned char blob1[] =
     "12346102356120394751634516591348710478123649165419234519234512349134";
 
 }  // namespace
 
 typedef BrowserWithTestWindowTest PrintPreviewUITest;
 
 // Create/Get a preview tab for initiator tab.
 TEST_F(PrintPreviewUITest, PrintPreviewData) {
-#if !defined(GOOGLE_CHROME_BUILD) || defined(OS_CHROMEOS) || defined(OS_MACOSX)
   CommandLine::ForCurrentProcess()->AppendSwitch(switches::kEnablePrintPreview);
-#endif
   ASSERT_TRUE(browser());
   BrowserList::SetLastActive(browser());
   ASSERT_TRUE(BrowserList::GetLastActive());
 
   browser()->NewTab();
   TabContents* initiator_tab = browser()->GetSelectedTabContents();
   ASSERT_TRUE(initiator_tab);
 
   scoped_refptr<printing::PrintPreviewTabController>
       controller(new printing::PrintPreviewTabController());
@@ skipping 18 matching lines @@
 
   preview_ui->SetPrintPreviewData(dummy_data.get());
   preview_ui->GetPrintPreviewData(&data);
   EXPECT_EQ(dummy_data->size(), data->size());
   EXPECT_EQ(dummy_data.get(), data.get());
 
   // This should not cause any memory leaks.
   dummy_data = new RefCountedBytes();
   preview_ui->SetPrintPreviewData(dummy_data);
 }