Remove special handling for strings in var serialization.

ppapi/shared_impl/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_SHARED_IMPL_VAR_H_
 #define PPAPI_SHARED_IMPL_VAR_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 76 matching lines @@
 //
 // Converting a PP_Var to a string:
 //   StringVar* string = StringVar::FromPPVar(var);
 //   if (!string)
 //     return false;  // Not a string or an invalid var.
 //   DoSomethingWithTheString(string->value());
 class PPAPI_SHARED_EXPORT StringVar : public Var {
  public:
   StringVar(const std::string& str);
   StringVar(const char* str, uint32 len);
-  StringVar(scoped_ptr<std::string> str);
   virtual ~StringVar();
 
   const std::string& value() const { return value_; }
   // Return a pointer to the internal string. This allows other objects to
   // temporarily store a weak pointer to our internal string. Use with care; the
   // pointer *will* become invalid if this StringVar is removed from the
   // tracker. (All of this applies to value(), but this one's even easier to use
   // dangerously).
   const std::string* ptr() const { return &value_; }
 
   // Var override.
   virtual StringVar* AsStringVar() OVERRIDE;
   virtual PP_VarType GetType() const OVERRIDE;
 
   // Helper function to create a PP_Var of type string that contains a copy of
   // the given string. The input data must be valid UTF-8 encoded text, if it
   // is not valid UTF-8, a NULL var will be returned.
   //
   // The return value will have a reference count of 1. Internally, this will
   // create a StringVar and return the reference to it in the var.
   static PP_Var StringToPPVar(const std::string& str);
   static PP_Var StringToPPVar(const char* str, uint32 len);
-  static PP_Var StringToPPVar(scoped_ptr<std::string> str);
+
+  // Same as StringToPPVar but avoids a copy by destructively swapping the
+  // given string into the newly created StringVar. The string must already be
+  // valid UTF-8. After the call, *src will be empty.
+  static PP_Var SwapValidatedUTF8StringIntoPPVar(std::string* src);
 
   // Helper function that converts a PP_Var to a string. This will return NULL
   // if the PP_Var is not of string type or the string is invalid.
   static StringVar* FromPPVar(PP_Var var);
 
  private:
+  StringVar();  // Makes an empty string.
+
   std::string value_;
 
   DISALLOW_COPY_AND_ASSIGN(StringVar);
 };
 
 // ArrayBufferVar --------------------------------------------------------------
 
 // Represents an array buffer Var.
 //
 // Note this is an abstract class. To create an appropriate concrete one, you
@@ skipping 23 matching lines @@
   // return NULL if the PP_Var is not of ArrayBuffer type.
   static ArrayBufferVar* FromPPVar(PP_Var var);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ArrayBufferVar);
 };
 
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_VAR_H_