Fix some WeakPtrFactory members that aren't last

ppapi/proxy/ppb_image_data_proxy.cc

Index: ppapi/proxy/ppb_image_data_proxy.cc
diff --git a/ppapi/proxy/ppb_image_data_proxy.cc b/ppapi/proxy/ppb_image_data_proxy.cc
index 0ed3c24a37a516d99ceffbdbf49cd42439f27a04..c9d61f9feae039505b9121dab1244f5f567e2925 100644
--- a/ppapi/proxy/ppb_image_data_proxy.cc
+++ b/ppapi/proxy/ppb_image_data_proxy.cc
@@ -249,15 +249,15 @@ class ImageDataCache {
   // Timer callback to expire entries for the given instance.
   void OnTimer(PP_Instance instance);
 
+  typedef std::map<PP_Instance, ImageDataInstanceCache> CacheMap;
+  CacheMap cache_;
+
   // This class does timer calls and we don't want to run these outside of the
   // scope of the object. Technically, since this class is a leaked static,
   // this will never happen and this factory is unnecessary. However, it's
   // probably better not to make assumptions about the lifetime of this class.
   base::WeakPtrFactory<ImageDataCache> weak_factory_;
 
-  typedef std::map<PP_Instance, ImageDataInstanceCache> CacheMap;
-  CacheMap cache_;
-
   DISALLOW_COPY_AND_ASSIGN(ImageDataCache);
 };