Fix issue with print preview on Chrome OS just displaying an error message.

printing/printing_context_cairo.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 "printing/printing_context_cairo.h"
 
 // TODO(abodenha@chromium.org) The number of #ifdefs here has gotten too
 // large.  Refactor this code into separate files for Linux and Chrome OS.
 
 #include "base/logging.h"
@@ skipping 130 matching lines @@
 }
 
 PrintingContext::Result PrintingContextCairo::UpdatePrinterSettings(
     const DictionaryValue& job_settings, const PageRanges& ranges) {
 #if defined(OS_CHROMEOS)
   bool landscape = false;
 
   if (!job_settings.GetBoolean(kSettingLandscape, &landscape))
     return OnError();
 
+  if (settings_.dpi() == 0)
+    UseDefaultSettings();
+
   settings_.SetOrientation(landscape);
   settings_.ranges = ranges;
 
   return OK;
 #else
   DCHECK(!in_print_job_);
 
   if (!print_dialog_) {
     print_dialog_ = create_dialog_func_(this);
     print_dialog_->AddRefToDialog();
@@ skipping 64 matching lines @@
 void PrintingContextCairo::ReleaseContext() {
   // Intentional No-op.
 }
 
 gfx::NativeDrawingContext PrintingContextCairo::context() const {
   // Intentional No-op.
   return NULL;
 }
 
 }  // namespace printing