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

ppapi/proxy/ppb_image_data_proxy.cc

Index: ppapi/proxy/ppb_image_data_proxy.cc
===================================================================
--- ppapi/proxy/ppb_image_data_proxy.cc	(revision 192603)
+++ ppapi/proxy/ppb_image_data_proxy.cc	(working copy)
@@ -431,20 +431,20 @@
 ImageHandle ImageData::NullHandle() {
 #if defined(OS_WIN)
   return NULL;
-#elif defined(OS_MACOSX) || defined(OS_ANDROID)
+#elif defined(TOOLKIT_GTK)
+  return 0;
+#else
   return ImageHandle();
-#else
-  return 0;
 #endif
 }
 
 ImageHandle ImageData::HandleFromInt(int32_t i) {
 #if defined(OS_WIN)
     return reinterpret_cast<ImageHandle>(i);
-#elif defined(OS_MACOSX) || defined(OS_ANDROID)
+#elif defined(TOOLKIT_GTK)
+    return static_cast<ImageHandle>(i);
+#else
     return ImageHandle(i, false);
-#else
-    return static_cast<ImageHandle>(i);
 #endif
 }
 #endif  // !defined(OS_NACL)