[Mac] Allow NSExceptions in certain cases.

printing/printing_context_mac.mm

 // 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_mac.h"
 
 #import <ApplicationServices/ApplicationServices.h>
 #import <AppKit/AppKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_cftyperef.h"
+#include "base/mac/scoped_nsautorelease_pool.h"
+#include "base/mac/scoped_nsexception_enabler.h"
 #include "base/sys_string_conversions.h"
 #include "base/values.h"
 #include "printing/print_settings_initializer_mac.h"
 
 static const CFStringRef kColorModel = CFSTR("ColorModel");
 static const CFStringRef kGrayColor = CFSTR("Gray");
 
 namespace printing {
 
 // static
 PrintingContext* PrintingContext::Create(const std::string& app_locale) {
   return static_cast<PrintingContext*>(new PrintingContextMac(app_locale));
 }
 
 PrintingContextMac::PrintingContextMac(const std::string& app_locale)
     : PrintingContext(app_locale),
       context_(NULL) {
 }
 
 PrintingContextMac::~PrintingContextMac() {
   ReleaseContext();
 }
 
 void PrintingContextMac::AskUserForSettings(gfx::NativeView parent_view,
                                             int max_pages,
                                             bool has_selection,
                                             PrintSettingsCallback* callback) {
+  // Third-party print drivers seem to be an area prone to raising exceptions.
+  // This will allow exceptions to be raised, but does not handle them.  The
+  // NSPrintPanel appears to have appropriate NSException handlers.
+  base::mac::ScopedNSExceptionEnabler enabler;
+
+  // Exceptions can also happen when the NSPrintPanel is being
+  // deallocated, so it must be autoreleased within this scope.
+  base::mac::ScopedNSAutoreleasePool pool;
+
   DCHECK([NSThread isMainThread]);
 
   // We deliberately don't feed max_pages into the dialog, because setting
   // NSPrintLastPage makes the print dialog pre-select the option to only print
   // a range.
 
   // TODO(stuartmorgan): implement 'print selection only' (probably requires
   // adding a new custom view to the panel on 10.5; 10.6 has
   // NSPrintPanelShowsPrintSelection).
   NSPrintPanel* panel = [NSPrintPanel printPanel];
@@ skipping 306 matching lines @@
 void PrintingContextMac::ReleaseContext() {
   print_info_.reset();
   context_ = NULL;
 }
 
 gfx::NativeDrawingContext PrintingContextMac::context() const {
   return context_;
 }
 
 }  // namespace printing