Avoid accessing VarTracker from multiple threads.

ppapi/proxy/serialized_var.h

 // Copyright (c) 2012 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.
 
 #ifndef PPAPI_PROXY_SERIALIZED_VAR_H_
 #define PPAPI_PROXY_SERIALIZED_VAR_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 83 matching lines @@
     ~Inner();
 
     VarSerializationRules* serialization_rules() {
       return serialization_rules_;
     }
     void set_serialization_rules(VarSerializationRules* serialization_rules) {
       serialization_rules_ = serialization_rules;
     }
 
     // See outer class's declarations above.
-    PP_Var GetVar() const;
+    PP_Var GetVar();
     void SetVar(PP_Var var);
 
     // For the SerializedVarTestConstructor, this writes the Var value as if
     // it was just received off the wire, without any serialization rules.
     void ForceSetVarValueForTest(PP_Var value);
 
     void WriteToMessage(IPC::Message* m) const;
     bool ReadFromMessage(const IPC::Message* m, PickleIterator* iter);
 
     // Sets the cleanup mode. See the CleanupMode enum below.
     void SetCleanupModeToEndSendPassRef();
     void SetCleanupModeToEndReceiveCallerOwned();
 
    private:
     enum CleanupMode {
       // The serialized var won't do anything special in the destructor
       // (default).
       CLEANUP_NONE,
 
       // The serialized var will call EndSendPassRef in the destructor.
       END_SEND_PASS_REF,
 
       // The serialized var will call EndReceiveCallerOwned in the destructor.
       END_RECEIVE_CALLER_OWNED
     };
 
+    // ReadFromMessage() may be called on the I/O thread, e.g., when reading the
+    // reply to a sync message. We cannot use the var tracker on the I/O thread,
+    // which means we cannot create PP_Var for PP_VARTYPE_STRING and
+    // PP_VARTYPE_ARRAY_BUFFER in ReadFromMessage(). So we save the raw var data
+    // and create PP_Var later when GetVar() is called, which should happen on
+    // the main thread.
+    struct RawVarData {
+      PP_VarType type;
+      std::string data;
+    };
+
+    // Converts |raw_var_data_| to |var_|. It is a no-op if |raw_var_data_| is
+    // NULL.
+    void ConvertRawVarData();
+
     // Rules for serializing and deserializing vars for this process type.
     // This may be NULL, but must be set before trying to serialize to IPC when
     // sending, or before converting back to a PP_Var when receiving.
     scoped_refptr<VarSerializationRules> serialization_rules_;
 
     // If this is set to VARTYPE_STRING and the 'value.id' is 0, then the
     // string_from_ipc_ holds the string. This means that the caller hasn't
     // called Deserialize with a valid Dispatcher yet, which is how we can
     // convert the serialized string value to a PP_Var string ID.
     //
     // This var may not be complete until the serialization rules are set when
     // reading from IPC since we'll need that to convert the string_value to
     // a string ID. Before this, the as_id will be 0 for VARTYPE_STRING.
     PP_Var var_;
 
     CleanupMode cleanup_mode_;
 
 #ifndef NDEBUG
     // When being sent or received over IPC, we should only be serialized or
     // deserialized once. These flags help us assert this is true.
     mutable bool has_been_serialized_;
     mutable bool has_been_deserialized_;
 #endif
 
+    // It will be non-NULL if there is PP_VARTYPE_STRING or
+    // PP_VARTYPE_ARRAY_BUFFER data from ReadFromMessage() that hasn't been
+    // converted to PP_Var.
+    scoped_ptr<RawVarData> raw_var_data_;
+
     DISALLOW_COPY_AND_ASSIGN(Inner);
   };
 
   SerializedVar(VarSerializationRules* serialization_rules);
 
   mutable scoped_refptr<Inner> inner_;
 };
 
 // Helpers for message sending side --------------------------------------------
 
@@ skipping 270 matching lines @@
   // The "incomplete" var is the one sent over the wire. Strings and object
   // IDs have not yet been converted, so this is the thing that tests will
   // actually want to check.
   PP_Var GetVar() const { return inner_->GetVar(); }
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_SERIALIZED_VAR_H_