Use WebFrame::replaceMisspelledRange() to replace a misspelled range with text.

chrome/common/spellcheck_messages.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.
 
 // IPC messages for spellcheck.
 // Multiply-included message file, hence no include guard.
 
 #include "chrome/common/spellcheck_result.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_platform_file.h"
@@ skipping 25 matching lines @@
 
 // A word has been added to the custom dictionary; update the local custom
 // word list.
 IPC_MESSAGE_CONTROL1(SpellCheckMsg_WordAdded,
                      std::string /* word */)
 
 // Toggle the auto spell correct functionality.
 IPC_MESSAGE_CONTROL1(SpellCheckMsg_EnableAutoSpellCorrect,
                      bool /* enable */)
 
+// Replace the selected misspelled range with the specified suggestion.
+IPC_MESSAGE_ROUTED1(SpellCheckMsg_Replace,
+                    string16)
+
 #if !defined(OS_MACOSX)
 // Sends text-check results from the Spelling service when the service finishes
 // checking text reveived by a SpellCheckHostMsg_CallSpellingService message.
 // If the service is not available, the 4th parameter should be false and
 // the 5th parameter should contain the requested setence.
 IPC_MESSAGE_ROUTED5(SpellCheckMsg_RespondSpellingService,
                     int         /* request identifier given by WebKit */,
                     int         /* offset */,
                     bool        /* succeeded calling serivce */,
                     string16    /* sentence */,
@@ skipping 70 matching lines @@
 IPC_MESSAGE_CONTROL4(SpellCheckHostMsg_RequestTextCheck,
                      int /* route_id for response */,
                      int /* request identifier given by WebKit */,
                      int /* document tag */,
                      string16 /* sentence */)
 
 IPC_MESSAGE_ROUTED2(SpellCheckHostMsg_ToggleSpellCheck,
                     bool /* enabled */,
                     bool /* checked */)
 #endif  // OS_MACOSX