sync: Finish non-blocking type encryption support

Undoes some previous work towards encryption support.  That approach
suffered from some subtle deadlock issues that could not be easily
worked around.  The new approach involves less sharing and less locks.

Gives the ModelTypeSyncWorker its own copy of the Cryptographer.  By
passing around copies, it no longer needs to worry about acquiring locks
in order to access the Directory's cryptographer.  This required
a rewrite of some changes to the way the ModelTypeSyncWorker detects the
current encryption state.  Most notably, its Cryptographer is NULL if
encryption is not enabled for its model type.

Makes the ModelTypeSyncRegistry responsible for observing changes
emitted by the SyncEncryptionHandler and forwarding them to the
ModelTypeSyncWorkers.  It should receive callbacks from the
SyncEncryptionHandler during startup, so it does not need to cache or
query any new data.

Removes the CryptographerProviders.  Since the ModelTypeSyncWorker no
longer need to access the directory's cryptographer, it's no longer
necessary.

BUG=351005

Review URL: https://codereview.chromium.org/452283003

Cr-Commit-Position: refs/heads/master@{#290067}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290067 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 0 insertions, 1 deletions

diff --git a/sync/protocol/proto_value_conversions.cc b/sync/protocol/proto_value_conversions.cc
index ba7fa53..62b611f 100644
--- a/sync/protocol/proto_value_conversions.cc
+++ b/sync/protocol/proto_value_conversions.cc
@@ -897,7 +897,6 @@ base::DictionaryValue* GetUpdateTriggersToValue(
   SET_BOOL(invalidations_out_of_sync);
   SET_INT64(local_modification_nudges);
   SET_INT64(datatype_refresh_nudges);
-  SET_BOOL(initial_sync_in_progress);
   return value;
 }