Move download extension api implementation to download/ dir.

chrome/browser/download/download_extension_api_constants.cc

 // 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.
 
-#include "chrome/browser/extensions/extension_downloads_api_constants.h"
+#include "chrome/browser/download/download_extension_api_constants.h"
 
-namespace extension_downloads_api_constants {
+namespace download_extension_api_constants {
 
 // Error messages
 const char kNotImplemented[] = "NotImplemented";
 const char kGenericError[] = "I'm afraid I can't do that.";
 const char kInvalidURL[] = "Invalid URL";
 
 // Parameter keys
 const char kBodyKey[] = "body";
 const char kBytesReceivedKey[] = "bytesReceived";
 const char kDangerAcceptedKey[] = "dangerAccepted";
@@ skipping 37 matching lines @@
     case DownloadItem::IN_PROGRESS: return kStateInProgress;
     case DownloadItem::COMPLETE: return kStateComplete;
     case DownloadItem::INTERRUPTED:  // fall through
     case DownloadItem::CANCELLED: return kStateInterrupted;
     case DownloadItem::REMOVING:  // fall through
     default:
       NOTREACHED();
       return "";
   }
 }
-}  // namespace extension_downloads_api_constants
+
+}  // namespace download_extension_api_constants