Implement a proxy for Pepper FileIO.

ppapi/proxy/ppb_file_ref_proxy.cc

Index: ppapi/proxy/ppb_file_ref_proxy.cc
diff --git a/ppapi/proxy/ppb_file_ref_proxy.cc b/ppapi/proxy/ppb_file_ref_proxy.cc
index 20b522ccf1f96d6a00fc3c59e00a96d4f4569ed2..e481f868b835930ba8e1e428f09e3f254ffb2283 100644
--- a/ppapi/proxy/ppb_file_ref_proxy.cc
+++ b/ppapi/proxy/ppb_file_ref_proxy.cc
@@ -33,6 +33,9 @@ class FileRef : public PPB_FileRef_Shared {
   explicit FileRef(const PPB_FileRef_CreateInfo& info);
   virtual ~FileRef();
 
+  // Resource overrides.
+  virtual void LastPluginRefWasDeleted() OVERRIDE;
+
   // PPB_FileRef_API implementation (not provided by PPB_FileRef_Shared).
   virtual PP_Resource GetParent() OVERRIDE;
   virtual int32_t MakeDirectory(PP_Bool make_ancestors,
@@ -77,6 +80,11 @@ FileRef::FileRef(const PPB_FileRef_CreateInfo& info)
 }
 
 FileRef::~FileRef() {
+  // The callbacks map should have been cleared by LastPluginRefWasDeleted.
+  DCHECK(pending_callbacks_.empty());
+}
+
+void FileRef::LastPluginRefWasDeleted() {
   // Abort all pending callbacks. Do this by posting a task to avoid reentering
   // the plugin's Release() call that probably deleted this object.
   for (PendingCallbackMap::iterator i = pending_callbacks_.begin();
@@ -85,6 +93,7 @@ FileRef::~FileRef() {
         i->second.func, i->second.user_data,
         static_cast<int32_t>(PP_ERROR_ABORTED)));
   }
+  pending_callbacks_.clear();
 }
 
 PP_Resource FileRef::GetParent() {