Adding a SQL implementation of the backing store for previews opt outs

chrome/common/chrome_constants.cc

Index: chrome/common/chrome_constants.cc
diff --git a/chrome/common/chrome_constants.cc b/chrome/common/chrome_constants.cc
index 0a96fa23db6edb6f24d10280467835d14871952e..b59b5230f20b352ea0c8d0e49467d09cfdfb1082 100644
--- a/chrome/common/chrome_constants.cc
+++ b/chrome/common/chrome_constants.cc
@@ -149,20 +149,22 @@ const base::FilePath::CharType kLocalStorePoolName[] = FPL("LocalStorePool");
 const base::FilePath::CharType kMediaCacheDirname[] = FPL("Media Cache");
 const base::FilePath::CharType kNetworkPersistentStateFilename[] =
     FPL("Network Persistent State");
 const base::FilePath::CharType kOfflinePageArchivesDirname[] =
     FPL("Offline Pages/archives");
 const base::FilePath::CharType kOfflinePageMetadataDirname[] =
     FPL("Offline Pages/metadata");
 const base::FilePath::CharType kOfflinePageRequestQueueDirname[] =
     FPL("Offline Pages/request_queue");
 const base::FilePath::CharType kPreferencesFilename[] = FPL("Preferences");
+const base::FilePath::CharType kPreviewsOptOutDirname[] =
+    FPL("Previews/opt_out");

[Scott Hess - ex-Googler, 2016/10/06 17:24:27]

Why a directory rather than a file?

[RyanSturm, 2016/10/06 20:05:39]

I was copying the Offline Page metadata approach, Done.

[Scott Hess - ex-Googler, 2016/10/07 00:08:45]

In that case ... I'll also question your use of kPreviewsColumns, TableInfo, and
OP_* column identifiers.  IMHO, those are not best practices.  In other areas of
the code, I find that that sort of thing somewhat obscures what is actually
going on, to no benefit.

[Yes, I have had this discussion with the Offline Page CLs.  They elected to go
forward as-is.]

[RyanSturm, 2016/10/07 20:07:05]

sgtm.

 const base::FilePath::CharType kProtectedPreferencesFilenameDeprecated[] =
     FPL("Protected Preferences");
 const base::FilePath::CharType kReadmeFilename[] = FPL("README");
 const base::FilePath::CharType kSafeBrowsingBaseFilename[] =
     FPL("Safe Browsing");
 const base::FilePath::CharType kSecurePreferencesFilename[] =
     FPL("Secure Preferences");
 const base::FilePath::CharType kServiceStateFileName[] = FPL("Service State");
 const base::FilePath::CharType kSingletonCookieFilename[] =
     FPL("SingletonCookie");