Move download extension api implementation to download/ dir.

chrome/browser/download/download_extension_api.h

Index: chrome/browser/download/download_extension_api.h
diff --git a/chrome/browser/extensions/extension_downloads_api.h b/chrome/browser/download/download_extension_api.h
similarity index 97%
rename from chrome/browser/extensions/extension_downloads_api.h
rename to chrome/browser/download/download_extension_api.h
index b0cf0e90cc3db310d6ae215aa9250fcfbb2156c4..183cf1f16d5d41766b06166b6c1d66badb07d960 100644
--- a/chrome/browser/extensions/extension_downloads_api.h
+++ b/chrome/browser/download/download_extension_api.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_DOWNLOADS_API_H_
-#define CHROME_BROWSER_EXTENSIONS_EXTENSION_DOWNLOADS_API_H_
+#ifndef CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSION_API_H_
+#define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSION_API_H_
 #pragma once
 
 #include <map>
@@ -274,4 +274,4 @@ class ExtensionDownloadsEventRouter : public DownloadManager::Observer {
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionDownloadsEventRouter);
 };
-#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_DOWNLOADS_API_H_
+#endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSION_API_H_