Switch Linux Auru ports over to POSIX SHM instead of legacy SYSV SHM.

ppapi/proxy/pdf_resource.cc

 // Copyright (c) 2013 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 "ppapi/proxy/pdf_resource.h"
 
 #include <stdlib.h>
 #include <string.h>
 
 #include "base/command_line.h"
@@ skipping 164 matching lines @@
   }
 
   if (resource.is_null())
     return 0;
   if (!PPB_ImageData_Shared::IsImageDataDescValid(image_desc))
     return 0;
 
 #if defined(OS_ANDROID)
   // This is compiled into android for tests only.
   return 0;
-#elif defined(OS_WIN) || defined(OS_MACOSX)
+#elif defined(TOOLKIT_GTK)
+  return (new ImageData(resource, image_desc, fd))->GetReference();
+#elif defined(OS_LINUX) || defined(OS_WIN) || defined(OS_MACOSX)
   base::SharedMemoryHandle handle;
   if (!reply_params.TakeSharedMemoryHandleAtIndex(0, &handle))
     return 0;
   return (new ImageData(resource, image_desc, handle))->GetReference();
-#elif defined(OS_LINUX)
-  return (new ImageData(resource, image_desc, fd))->GetReference();
 #else
 #error Not implemented.
 #endif
 }
 
 PP_Resource PDFResource::GetResourceImage(PP_ResourceImage image_id) {
   return GetResourceImageForScale(image_id, 1.0f);
 }
 
 }  // namespace proxy
 }  // namespace ppapi