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

components/previews/core/previews_black_list.cc

Index: components/previews/core/previews_black_list.cc
diff --git a/components/previews/core/previews_black_list.cc b/components/previews/core/previews_black_list.cc
index f4b277b6f231ee0f0e6b4dca36c274bd30b29f94..e991130c5cedb37555281246d93c16fa3c0a2752 100644
--- a/components/previews/core/previews_black_list.cc
+++ b/components/previews/core/previews_black_list.cc
@@ -14,31 +14,33 @@
 #include "url/gurl.h"
 
 namespace previews {
 
 PreviewsBlackList::PreviewsBlackList(
     std::unique_ptr<PreviewsOptOutStore> opt_out_store,
     std::unique_ptr<base::Clock> clock)
     : loaded_(false),
       opt_out_store_(std::move(opt_out_store)),
       clock_(std::move(clock)),
-      weak_factory_(this) {
+      weak_factory_(this) {}
+
+PreviewsBlackList::~PreviewsBlackList() {}
+
+void PreviewsBlackList::Initialize() {

[tbansal1, 2016/10/04 15:01:21]

Add thread checker.

[RyanSturm, 2016/10/04 19:10:23]

I'm undoing this. It doesn't actually help anything.

   if (opt_out_store_) {
     opt_out_store_->LoadBlackList(base::Bind(
         &PreviewsBlackList::LoadBlackListDone, weak_factory_.GetWeakPtr()));
   } else {
     LoadBlackListDone(base::MakeUnique<BlackListItemMap>());
   }
 }
 
-PreviewsBlackList::~PreviewsBlackList() {}
-
 void PreviewsBlackList::AddPreviewNavigation(const GURL& url,
                                              bool opt_out,
                                              PreviewsType type) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(url.has_host());
   // If the |black_list_item_map_| has been loaded from |opt_out_store_|,
   // synchronous operations will be accurate. Otherwise, queue the task to run
   // asynchronously.
   if (loaded_) {
     AddPreviewNavigationSync(url, opt_out, type);