Pepper: Clean up trusted plugin arguments.

ppapi/native_client/src/trusted/plugin/plugin.h

Index: ppapi/native_client/src/trusted/plugin/plugin.h
diff --git a/ppapi/native_client/src/trusted/plugin/plugin.h b/ppapi/native_client/src/trusted/plugin/plugin.h
index 3c176984d187e58ef9bf0a8292a3add721558419..fb4c0de933e3c5050ae035936a6a8371183751b4 100644
--- a/ppapi/native_client/src/trusted/plugin/plugin.h
+++ b/ppapi/native_client/src/trusted/plugin/plugin.h
@@ -122,8 +122,7 @@ class Plugin : public pp::InstancePrivate {
                                        ErrorInfo* error_info);
 
   // Returns the argument value for the specified key, or NULL if not found.
-  // The callee retains ownership of the result.
-  char* LookupArgument(const char* key);
+  std::string LookupArgument(const std::string& key) const;
 
   enum LengthComputable {
     LENGTH_IS_NOT_COMPUTABLE = 0,
@@ -393,9 +392,7 @@ class Plugin : public pp::InstancePrivate {
 
   ScriptablePlugin* scriptable_plugin_;
 
-  int argc_;
-  char** argn_;
-  char** argv_;
+  std::map<std::string, std::string> args_;
 
   // Keep track of the NaCl module subprocess that was spun up in the plugin.
   NaClSubprocess main_subprocess_;