Printing: Push checking of |context| one level lower, as the different

printing/printed_document_mac.cc

 // Copyright (c) 2009 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 "printing/printed_document.h"
 
 #import <ApplicationServices/ApplicationServices.h>
 #import <CoreFoundation/CoreFoundation.h>
 
 #include "base/logging.h"
 #include "base/scoped_cftyperef.h"
 #include "printing/page_number.h"
 #include "printing/printed_page.h"
 
 namespace printing {
 
 void PrintedDocument::RenderPrintedPage(
     const PrintedPage& page, gfx::NativeDrawingContext context) const {
 #ifndef NDEBUG
   {
     // Make sure the page is from our list.
     AutoLock lock(lock_);
     DCHECK(&page == mutable_.pages_.find(page.page_number() - 1)->second.get());
   }
 #endif
 
+  DCHECK(context);
+
   const printing::PageSetup& page_setup(
       immutable_.settings_.page_setup_device_units());
   gfx::Rect content_area;
   page.GetCenteredPageContentRect(page_setup.physical_size(), &content_area);
 
   const printing::NativeMetafile* metafile = page.native_metafile();
   // Each NativeMetafile is a one-page PDF, and pages use 1-based indexing.
   const int page_number = 1;
   metafile->RenderPage(page_number, context, content_area.ToCGRect(),
                        true, false, false, false);
 
   // TODO(stuartmorgan): Print the header and footer.
 }
 
 }  // namespace printing