sync: Add non-blocking type encryption (retry)

sync: Add non-blocking type encryption (retry)

Fixes some memory leak issues that were present in the first instance
of this CL.  Original description follows:

Introduces the framework for dealing with sync encryption in
non-blocking types.  Unlike directory sync types, non-blocking type
encryption only encrypts data before it is sent to the server.
Encrypting the data on-disk is a separate problem.

Adds code to the ModelTypeSyncWorker so it can access the directory's
cryptographer (through a CryptographerProvider interface) and use it to
encrypt entities before it sends them to the server.  If the
cryptographer is unable to encrypt with the desired key, the worker will
not commit until the cryptographer returns to a good state.

Adds the concept of a "desired encryption key" to the data type state.
When the cryptographer key to be used to encrypt a type changes, this
will be reflected in the data type state.  The ModelTypeSyncProxy is
responsible for ensuring that all items which have not yet been
encrypted with this desired key are enqueued for commit.

Makes the ModelTypeSyncWorker, EntityTracker, and ModelTypeSyncProxy
collaborate on the management of undecryptable (inapplicable) updates.
The EntityTracker keeps track of their version numbers and content, and
prevents the committing of new items to the server until the
inapplicable update has been dealt with.  The ModelTypeSyncProxy is
responsible for saving inapplicable updates across restarts.

This CL alone is not enough to enable encryption support for
non-blocking types.  It requires additional code to hook up the
ModelTypeSyncWorkers to receive cryptographer events.  This will be
added in a future commit.  In the meantime, this CL includes plenty
of unit tests to verify the functionality that's being added.

BUG=351005
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=287849

[rlarocque, 2014-08-05 18:58:01]

I forgot to upload the original to highlight the fixes.  Fortunately, the diff
is small, so I can just post it here:

diff --git a/sync/engine/model_type_sync_proxy_impl_unittest.cc
b/sync/engine/model_type_sync_proxy_impl_unittest.cc
index 581d511..860cc70 100644
--- a/sync/engine/model_type_sync_proxy_impl_unittest.cc
+++ b/sync/engine/model_type_sync_proxy_impl_unittest.cc
@@ -567,6 +567,8 @@ TEST_F(ModelTypeSyncProxyImplTest, Disable) {
 
 // Test receipt of pending updates.
 TEST_F(ModelTypeSyncProxyImplTest, ReceivePendingUpdates) {
+  InitializeToReadyState();
+
   EXPECT_FALSE(HasPendingUpdate("tag1"));
   EXPECT_EQ(0U, GetNumPendingUpdates());
 
@@ -596,6 +598,8 @@ TEST_F(ModelTypeSyncProxyImplTest, ReceivePendingUpdates) {
 
 // Test that Disable clears pending update state.
 TEST_F(ModelTypeSyncProxyImplTest, DisableWithPendingUpdates) {
+  InitializeToReadyState();
+
   PendingUpdateFromServer(5, "tag1", "value1", "key1");
   EXPECT_EQ(1U, GetNumPendingUpdates());
   ASSERT_TRUE(HasPendingUpdate("tag1"));
@@ -609,6 +613,8 @@ TEST_F(ModelTypeSyncProxyImplTest,
DisableWithPendingUpdates) {
 
 // Test that Disconnect does not clear pending update state.
 TEST_F(ModelTypeSyncProxyImplTest, DisconnectWithPendingUpdates) {
+  InitializeToReadyState();
+
   PendingUpdateFromServer(5, "tag1", "value1", "key1");
   EXPECT_EQ(1U, GetNumPendingUpdates());
   ASSERT_TRUE(HasPendingUpdate("tag1"));

It adds some calls to InitializeToReadyState() that were necessary to pass
ownership of the ModelTypeSyncWorker to its proper owner.

[rlarocque, 2014-08-05 19:40:22]

First attempt got reverted.  Here's the retry.

See previous message in this CL for the diff.

Please review.

[Nicolas Zea, 2014-08-06 18:58:41]

lgtm

[rlarocque, 2014-08-06 18:59:21]

The CQ bit was checked by rlarocque@chromium.org

[commit-bot: I haz the power, 2014-08-06 19:01:12]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/rlarocque@chromium.org/442053002/1

[commit-bot: I haz the power, 2014-08-06 20:46:21]

Change committed as 287849