Convert resources to take an instance key instead of an Instance*.

ppapi/cpp/module.h

 // Copyright (c) 2011 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_CPP_MODULE_H_
 #define PPAPI_CPP_MODULE_H_
 
 #include <map>
 #include <string>
 
@@ skipping 68 matching lines @@
   ///
   /// @param[in] interface_name The module interface for the browser to get.
   const void* GetPluginInterface(const char* interface_name);
 
   /// GetBrowserInterface() returns interfaces which the browser implements
   /// (i.e. PPB interfaces).
   /// @param[in] interface_name The browser interface for the moduel to get.
   const void* GetBrowserInterface(const char* interface_name);
 
   /// InstanceForPPInstance() returns the object associated with this
-  /// <code>PP_Instance</code>, or NULL if one is not found.
+  /// <code>PP_Instance</code>, or NULL if one is not found. This should only
+  /// be called from the main thread! This instance object may be destroyed at
+  /// any time on the main thread, so using it on other threads may cause a
+  /// crash.
   ///
   /// @param[in] instance This <code>PP_Instance</code>.
   ///
   /// @return The object associated with this <code>PP_Instance</code>,
   /// or NULL if one is not found.
   Instance* InstanceForPPInstance(PP_Instance instance);
 
   /// AddPluginInterface() adds a handler for a provided interface name. When
   /// the browser requests that interface name, the provided
   /// <code>vtable</code> will be returned.
@@ skipping 62 matching lines @@
 
   // All additional interfaces this plugin can handle as registered by
   // AddPluginInterface.
   typedef std::map<std::string, const void*> InterfaceMap;
   InterfaceMap additional_interfaces_;
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_MODULE_H_