Add the download component and initial setup

chrome/common/chrome_constants.h

Index: chrome/common/chrome_constants.h
diff --git a/chrome/common/chrome_constants.h b/chrome/common/chrome_constants.h
index a0c67803c3454c2ea3d7a67e1b1f084d17ef4abd..e606308062e3a6635594505c228c338c0d068051 100644
--- a/chrome/common/chrome_constants.h
+++ b/chrome/common/chrome_constants.h
@@ -48,6 +48,8 @@ extern const base::FilePath::CharType kChannelIDFilename[];
 extern const base::FilePath::CharType kCookieFilename[];
 extern const base::FilePath::CharType kCRLSetFilename[];
 extern const base::FilePath::CharType kCustomDictionaryFileName[];
+extern const base::FilePath::CharType kDownloadServicePersistedStorageDirname[];
+extern const base::FilePath::CharType kDownloadServiceTemporaryStorageDirname[];

[xingliu, 2017/05/01 23:56:54]

Shall we remove it or define this in chrome_constants.cc?

[Peter Beverloo, 2017/05/02 16:12:20]

+1 to removing, it's unused

[David Trainor- moved to gerrit, 2017/05/03 06:02:58]

Thanks!  My bad I forgot to remove the header definition.

 extern const base::FilePath::CharType kExtensionActivityLogFilename[];
 extern const base::FilePath::CharType kExtensionsCookieFilename[];
 extern const base::FilePath::CharType kFeatureEngagementTrackerStorageDirname[];