[PPAPI] Fix a bunch of spelling mistakes

ppapi/cpp/private/var_private.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_PRIVATE_VAR_PRIVATE_H_
 #define PPAPI_CPP_PRIVATE_VAR_PRIVATE_H_
 
 #include "ppapi/cpp/var.h"
 
 namespace pp {
 
 class InstanceHandle;
 
 namespace deprecated {
 class ScriptableObject;
 }
 
 // VarPrivate is a version of Var that exposes the private scripting API.
-// It's designed to be mostly interchangable with Var since most callers will
+// It's designed to be mostly interchangeable with Var since most callers will
 // be dealing with Vars from various places.
 class VarPrivate : public Var {
  public:
   VarPrivate() : Var() {}
   VarPrivate(Null) : Var(Null()) {}
   VarPrivate(bool b) : Var(b) {}
   VarPrivate(int32_t i) : Var(i) {}
   VarPrivate(double d) : Var(d) {}
   VarPrivate(const char* utf8_str) : Var(utf8_str) {}
   VarPrivate(const std::string& utf8_str) : Var(utf8_str) {}
@@ skipping 85 matching lines @@
  private:
   // Prevent an arbitrary pointer argument from being implicitly converted to
   // a bool at Var construction. If somebody makes such a mistake, (s)he will
   // get a compilation error.
   VarPrivate(void* non_scriptable_object_pointer);
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_PRIVATE_VAR_PRIVATE_H_