[Sync] Add support for server-controlled favicon sync limit

This allows us to adjust the number of favicons clients will maintain
as we determine how well we handle them.

BUG=154886

Review URL: https://chromiumcodereview.appspot.com/14117004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@195074 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/sync/glue/favicon_cache.cc

@@ -225,6 +225,7 @@ FaviconCache::FaviconCache(Profile* profile, int max_sync_favicon_limit)
   notification_registrar_.Add(this,
                               chrome::NOTIFICATION_HISTORY_URLS_DELETED,
                               content::Source<Profile>(profile_));
+  DVLOG(1) << "Setting favicon limit to " << max_sync_favicon_limit;
 }
 
 FaviconCache::~FaviconCache() {}

chrome/browser/sync/glue/session_model_associator.cc

@@ -103,7 +103,8 @@ SessionModelAssociator::SessionModelAssociator(
       ALLOW_THIS_IN_INITIALIZER_LIST(test_weak_factory_(this)),
       profile_(sync_service->profile()),
       error_handler_(error_handler),
-      favicon_cache_(profile_, kMaxSyncFavicons) {
+      favicon_cache_(profile_,
+                     sync_service->current_experiments().favicon_sync_limit) {
   DCHECK(CalledOnValidThread());
   DCHECK(sync_service_);
   DCHECK(profile_);

sync/internal_api/public/util/experiments.h

@@ -22,13 +22,15 @@ struct Experiments {
   Experiments() : keystore_encryption(false),
                   autofill_culling(false),
                   full_history_sync(false),
-                  favicon_sync(false) {}
+                  favicon_sync(false),
+                  favicon_sync_limit(200) {}
 
   bool Matches(const Experiments& rhs) {
     return (keystore_encryption == rhs.keystore_encryption &&
             autofill_culling == rhs.autofill_culling &&
             full_history_sync == rhs.full_history_sync &&
-            favicon_sync == rhs.favicon_sync);
+            favicon_sync == rhs.favicon_sync &&
+            favicon_sync_limit == rhs.favicon_sync_limit);
   }
 
   // Enable keystore encryption logic and the new encryption UI.
@@ -42,6 +44,9 @@ struct Experiments {
 
   // Enable the favicons sync datatypes (favicon images and favicon tracking).
   bool favicon_sync;
+
+  // The number of favicons that a client is permitted to sync.
+  int favicon_sync_limit;
 };
 
 }  // namespace syncer

sync/internal_api/sync_manager_impl.cc

@@ -1379,9 +1379,12 @@ bool SyncManagerImpl::ReceivedExperiment(Experiments* experiments) {
   ReadNode favicon_sync_node(&trans);
   if (favicon_sync_node.InitByClientTagLookup(
           syncer::EXPERIMENTS,
-          syncer::kFaviconSyncTag) == BaseNode::INIT_OK &&
-      favicon_sync_node.GetExperimentsSpecifics().favicon_sync().enabled()) {
-    experiments->favicon_sync = true;
+          syncer::kFaviconSyncTag) == BaseNode::INIT_OK) {
+    experiments->favicon_sync = favicon_sync_node.GetExperimentsSpecifics().
+        favicon_sync().enabled();
+    experiments->favicon_sync_limit =
+        favicon_sync_node.GetExperimentsSpecifics().favicon_sync().
+            favicon_sync_limit();
     found_experiment = true;
   }
 

sync/protocol/experiments_specifics.proto

@@ -27,9 +27,11 @@ message AutofillCullingFlags {
   optional bool enabled = 1;
 }
 
-// Whether the favicon sync datatypes are enabled.
+// Whether the favicon sync datatypes are enabled, and what parameters
+// they should operate under.
 message FaviconSyncFlags {
   optional bool enabled = 1;
+  optional int32 favicon_sync_limit = 2 [default = 200];
 }
 
 // Contains one flag or set of related flags.  Each node of the experiments type

sync/protocol/proto_value_conversions.cc

@@ -332,13 +332,26 @@ base::DictionaryValue* DictionarySpecificsToValue(
   return value;
 }
 
+namespace {
+
+DictionaryValue* FaviconSyncFlagsToValue(
+    const sync_pb::FaviconSyncFlags& proto) {
+  base::DictionaryValue* value = new base::DictionaryValue();
+  SET_BOOL(enabled);
+  SET_INT32(favicon_sync_limit);
+  return value;
+}
+
+}
+
 base::DictionaryValue* ExperimentsSpecificsToValue(
     const sync_pb::ExperimentsSpecifics& proto) {
   base::DictionaryValue* value = new base::DictionaryValue();
   SET_EXPERIMENT_ENABLED_FIELD(keystore_encryption);
   SET_EXPERIMENT_ENABLED_FIELD(history_delete_directives);
   SET_EXPERIMENT_ENABLED_FIELD(autofill_culling);
-  SET_EXPERIMENT_ENABLED_FIELD(favicon_sync);
+  if (proto.has_favicon_sync())
+    SET(favicon_sync, FaviconSyncFlagsToValue);
   return value;
 }