Download Service : Added leveldb proto layer

Download Service : Added leveldb proto layer

Added DownloadStore which is a layer around a leveldb ProtoDatabase that
stores download params, scheduling params, request headers and various
metadata as protos. Callers of DownloadStore expect a list of Entry's,
hence conversion utility methods were added to convert between Entry
and protodb::Entry.

Other details:
1- Moved NoopStore to download/internal/test/
2- Replaced usage of OnceCallback with repeated Callback, since the
proto database expects repeated Callback. In order to change ProtoDatabase
to use OnceCallback, it probably requires a larger change invloving
changing the client sites of ProtoDatabase.

BUG=722705
Review-Url: https://codereview.chromium.org/2881173003
Cr-Commit-Position: refs/heads/master@{#475750}
Committed: https://chromium.googlesource.com/chromium/src/+/ca5a950a9da72f942db32e10751f459584998c22

[shaktisahu, 2017-05-16 04:59:27]

Description was changed from

==========
Download Service : Added leveldb proto layer

BUG=722705
==========

to

==========
Download Service : Added leveldb proto layer

BUG=722705
==========

[shaktisahu, 2017-05-16 04:59:27]

shaktisahu@chromium.org changed reviewers:
+ dtrainor@chromium.org

[shaktisahu, 2017-05-16 05:04:06]

This is not complete, but could you give some high level feedback? 

TODO : Write the proto conversions for all the methods.
TODO : More tests.

[shaktisahu, 2017-05-17 22:21:18]

Patchset #2 (id:20001) has been deleted

[shaktisahu, 2017-05-17 22:41:34]

Description was changed from

==========
Download Service : Added leveldb proto layer

BUG=722705
==========

to

==========
Download Service : Added leveldb proto layer

Added DownloadStore which is a layer around a leveldb ProtoDatabase that
stores download params, scheduling params, request headers and various
metadata as protos. Callers of DownloadStore expect a list of Entry's,
hence conversion utility methods were added to convert between Entry
and protodb::Entry.

Other details:
1- Moved NoopStore to download/internal/test/
2- Replaced usage of OnceCallback with repeated Callback, since the
proto database expects repeated Callback. In order to change ProtoDatabase
to use OnceCallback, it probably requires a larger change invloving
changing the client sites of ProtoDatabase.

BUG=722705
==========

[shaktisahu, 2017-05-17 23:49:11]

PTAL

[David Trainor- moved to gerrit, 2017-05-18 19:41:01]

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/download_store.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store.cc:15: namespace {
Put this inside namespace download too?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store.cc:19: using EntryVector =
std::vector<protodb::Entry>;
ProtoEntryVector?  EntryVector sounds like std::vector<Entry>

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/download_store_unittest.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:29: ~DownloadStoreTest()
override {}
= default?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:39: void
InitCallback(std::vector<Entry>* loaded_entries,
Do you need both of these?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:42: //
ASSERT_TRUE(success);
?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:49: //
ASSERT_TRUE(success);
?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/proto/entry.proto (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/entry.proto:13: enum DownloadClient {
Comment about keeping this in sync with the list in clients.h?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/entry.proto:25: message RequestParams {
If we pulled out scheduling we should pull this out as well.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/entry.proto:34: enum State {
Comment about keeping this in sync with the state in entry.h?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/proto/scheduling.proto (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/scheduling.proto:14: enum NetworkRequirements
{
Same as other file, point to where these are in code and say we need to keep
them in sync/order shouldn't change.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/scheduling.proto:34: optional int64
cancel_time = 2;
Give this a unit?  utc?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/proto_conversions.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto_conversions.cc:158:
base::Time::FromInternalValue(proto.cancel_time());
Is this how these are generally saved in Chrome?  Does it make sense to convert
to a standard time format?

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/store.h (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/store.h:22: base::Callback<void(bool success,
Sadness! :(

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/test/entry_utils.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/test/entry_utils.cc:12: bool
SuperficialEntryCompare(const Entry* const& expected,
This compare is no longer superficial.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/test/entry_utils.cc:65: Entry entry;
Call BuildEntry(client, guid) and then set the rest?

[shaktisahu, 2017-05-19 04:54:58]

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/download_store.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store.cc:15: namespace {
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Put this inside namespace download too?

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store.cc:19: using EntryVector =
std::vector<protodb::Entry>;
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> ProtoEntryVector?  EntryVector sounds like std::vector<Entry>

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/download_store_unittest.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:29: ~DownloadStoreTest()
override {}
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> = default?

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:39: void
InitCallback(std::vector<Entry>* loaded_entries,
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Do you need both of these?

I need two functions for two different purposes. One for passing to
store_->Initialize(callback..) and another when querying the actual database
db_->UpdateEntries(callback...)
One of them populates a vector of Entry while the other one populates vector of
protodb::Entry

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:42: //
ASSERT_TRUE(success);
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> ?

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/download_store_unittest.cc:49: //
ASSERT_TRUE(success);
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> ?

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/proto/entry.proto (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/entry.proto:13: enum DownloadClient {
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Comment about keeping this in sync with the list in clients.h?

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/entry.proto:25: message RequestParams {
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> If we pulled out scheduling we should pull this out as well.

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/entry.proto:34: enum State {
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Comment about keeping this in sync with the state in entry.h?

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/proto/scheduling.proto (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/scheduling.proto:14: enum NetworkRequirements
{
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Same as other file, point to where these are in code and say we need to keep
> them in sync/order shouldn't change.

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto/scheduling.proto:34: optional int64
cancel_time = 2;
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Give this a unit?  utc?

Done.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/proto_conversions.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/proto_conversions.cc:158:
base::Time::FromInternalValue(proto.cancel_time());
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Is this how these are generally saved in Chrome?  Does it make sense to
convert
> to a standard time format?

Yes, this is how it is stored in the download history database.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
File components/download/internal/test/entry_utils.cc (right):

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/test/entry_utils.cc:12: bool
SuperficialEntryCompare(const Entry* const& expected,
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> This compare is no longer superficial.

Done. Renamed to CompareEntry.

https://codereview.chromium.org/2881173003/diff/60001/components/download/int...
components/download/internal/test/entry_utils.cc:65: Entry entry;
On 2017/05/18 19:41:00, David Trainor-ping if over 24h wrote:
> Call BuildEntry(client, guid) and then set the rest?

Done.

[David Trainor- moved to gerrit, 2017-05-19 19:07:06]

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
File components/download/internal/download_store.cc (right):

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
components/download/internal/download_store.cc:15: namespace {
I meant whole anonymous namespace :D

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
File components/download/internal/proto/scheduling.proto (right):

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
components/download/internal/proto/scheduling.proto:37: optional int64
cancel_time_utc = 2;
utc_ms or something?

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
File components/download/internal/proto_conversions.cc (right):

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
components/download/internal/proto_conversions.cc:158:
base::Time::FromInternalValue(proto.cancel_time_utc());
Hmm if this is how we store it there and we're going to use that method, does it
actually represent UTC?  Might be cleaner to migrate it to and from a common
unit?

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
File components/download/internal/test/entry_utils.cc (right):

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
components/download/internal/test/entry_utils.cc:12: bool CompareEntry(const
Entry* const& expected, const Entry* const& actual) {
Might just be worth adding an == operator to Entry at this point.  Maybe add a
TODO and file a bug?

[shaktisahu, 2017-05-19 21:33:16]

Patchset #5 (id:100001) has been deleted

[shaktisahu, 2017-05-20 03:35:58]

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
File components/download/internal/download_store.cc (right):

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
components/download/internal/download_store.cc:15: namespace {
On 2017/05/19 19:07:05, David Trainor-ping if over 24h wrote:
> I meant whole anonymous namespace :D

Done.

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
File components/download/internal/proto/scheduling.proto (right):

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
components/download/internal/proto/scheduling.proto:37: optional int64
cancel_time_utc = 2;
On 2017/05/19 19:07:05, David Trainor-ping if over 24h wrote:
> utc_ms or something?

Done.

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
File components/download/internal/proto_conversions.cc (right):

https://codereview.chromium.org/2881173003/diff/80001/components/download/int...
components/download/internal/proto_conversions.cc:158:
base::Time::FromInternalValue(proto.cancel_time_utc());
On 2017/05/19 19:07:06, David Trainor-ping if over 24h wrote:
> Hmm if this is how we store it there and we're going to use that method, does
it
> actually represent UTC?  Might be cleaner to migrate it to and from a common
> unit?

Done.

[David Trainor- moved to gerrit, 2017-05-23 06:18:00]

lgtm

https://codereview.chromium.org/2881173003/diff/120001/components/download/in...
File components/download/internal/download_store.cc (right):

https://codereview.chromium.org/2881173003/diff/120001/components/download/in...
components/download/internal/download_store.cc:16: const char
kDatabaseClientName[] = "DownloadService";
put these in an anonymous namespace inside download:

namespace download {
namespace {
...
}  // namespace
...
}  // namespace download

[shaktisahu, 2017-05-23 20:51:10]

The CQ bit was checked by shaktisahu@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-23 20:52:18]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-23 20:57:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-23 20:57:43]

Dry run: Try jobs failed on following builders:
  android_compile_dbg on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_comp...)
  android_cronet on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_cron...)
  cast_shell_android on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/cast_shell_a...)
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)
  linux_chromium_asan_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[shaktisahu, 2017-05-23 21:13:22]

The CQ bit was checked by shaktisahu@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-23 21:13:55]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-23 21:42:53]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-23 21:42:54]

Dry run: Try jobs failed on following builders:
  android_n5x_swarming_rel on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_...)
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)

[shaktisahu, 2017-05-23 23:34:58]

The CQ bit was checked by shaktisahu@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-23 23:36:24]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-24 05:08:26]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-24 05:08:27]

Dry run: Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)

[shaktisahu, 2017-05-24 15:08:37]

The CQ bit was checked by shaktisahu@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-24 15:09:18]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-24 15:16:31]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-24 15:16:32]

Dry run: Try jobs failed on following builders:
  linux_android_rel_ng on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_androi...)
  chromium_presubmit on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[David Trainor- moved to gerrit, 2017-05-24 15:31:21]

https://codereview.chromium.org/2881173003/diff/180001/components/download/in...
File components/download/internal/store.h (right):

https://codereview.chromium.org/2881173003/diff/180001/components/download/in...
components/download/internal/store.h:39: virtual void Destroy(const
StoreCallback& callback) = 0;
Let's remove this... I think I misunderstood what this does.  nyquist@ pointed
out that this deletes the database! :(  Check and remove if so.  Thanks!

[shaktisahu, 2017-05-24 18:05:46]

Patchset #6 (id:140001) has been deleted

[shaktisahu, 2017-05-24 18:05:58]

Patchset #6 (id:160001) has been deleted

[shaktisahu, 2017-05-24 18:15:12]

Patchset #8 (id:220001) has been deleted

[shaktisahu, 2017-05-24 18:15:49]

The CQ bit was checked by shaktisahu@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-24 18:16:47]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[shaktisahu, 2017-05-24 18:29:01]

https://codereview.chromium.org/2881173003/diff/180001/components/download/in...
File components/download/internal/store.h (right):

https://codereview.chromium.org/2881173003/diff/180001/components/download/in...
components/download/internal/store.h:39: virtual void Destroy(const
StoreCallback& callback) = 0;
On 2017/05/24 15:31:21, David Trainor-ping if over 24h wrote:
> Let's remove this... I think I misunderstood what this does.  nyquist@ pointed
> out that this deletes the database! :(  Check and remove if so.  Thanks!

Yes, this would delete the database. Removed.

[David Trainor- moved to gerrit, 2017-05-24 19:17:31]

lgtm % nit

https://codereview.chromium.org/2881173003/diff/240001/components/download/in...
File components/download/internal/model_impl.cc (right):

https://codereview.chromium.org/2881173003/diff/240001/components/download/in...
components/download/internal/model_impl.cc:27: void ModelImpl::Destroy() {
Just get rid of this as well!

[shaktisahu, 2017-05-24 20:28:31]

The CQ bit was checked by shaktisahu@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-24 20:29:00]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[shaktisahu, 2017-05-24 22:01:51]

The CQ bit was unchecked by shaktisahu@chromium.org

[shaktisahu, 2017-05-24 22:01:53]

The CQ bit was checked by shaktisahu@chromium.org

[shaktisahu, 2017-05-24 22:01:54]

The patchset sent to the CQ was uploaded after l-g-t-m from
dtrainor@chromium.org
Link to the patchset: https://codereview.chromium.org/2881173003/#ps260001
(title: "Removed Model::Destroy")

[commit-bot: I haz the power, 2017-05-24 22:02:26]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-24 22:13:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-24 22:13:43]

Try jobs failed on following builders:
  chromium_presubmit on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[shaktisahu, 2017-05-24 22:20:43]

shaktisahu@chromium.org changed reviewers:
+ nyquist@chromium.org

[shaktisahu, 2017-05-24 22:20:44]

nyquist@ - I need OWNERS approval for using components/leveldb_proto. PTAL

[nyquist, 2017-05-30 20:18:16]

components/leveldb_proto DEPS lgtm

[shaktisahu, 2017-05-30 23:15:56]

The CQ bit was checked by shaktisahu@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-05-30 23:16:49]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[shaktisahu, 2017-05-31 00:03:50]

The CQ bit was unchecked by shaktisahu@chromium.org

[shaktisahu, 2017-05-31 00:03:56]

The CQ bit was checked by shaktisahu@chromium.org

[commit-bot: I haz the power, 2017-05-31 00:04:42]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-31 02:28:38]

CQ is committing da patch.

Bot data: {"patchset_id": 260001, "attempt_start_ts": 1496189036873030,
"parent_rev": "e2381bcbf4a7ea39be7298af2745cc0c8627ea40", "commit_rev":
"ca5a950a9da72f942db32e10751f459584998c22"}

[commit-bot: I haz the power, 2017-05-31 02:28:47]

Description was changed from

==========
Download Service : Added leveldb proto layer

Added DownloadStore which is a layer around a leveldb ProtoDatabase that
stores download params, scheduling params, request headers and various
metadata as protos. Callers of DownloadStore expect a list of Entry's,
hence conversion utility methods were added to convert between Entry
and protodb::Entry.

Other details:
1- Moved NoopStore to download/internal/test/
2- Replaced usage of OnceCallback with repeated Callback, since the
proto database expects repeated Callback. In order to change ProtoDatabase
to use OnceCallback, it probably requires a larger change invloving
changing the client sites of ProtoDatabase.

BUG=722705
==========

to

==========
Download Service : Added leveldb proto layer

Added DownloadStore which is a layer around a leveldb ProtoDatabase that
stores download params, scheduling params, request headers and various
metadata as protos. Callers of DownloadStore expect a list of Entry's,
hence conversion utility methods were added to convert between Entry
and protodb::Entry.

Other details:
1- Moved NoopStore to download/internal/test/
2- Replaced usage of OnceCallback with repeated Callback, since the
proto database expects repeated Callback. In order to change ProtoDatabase
to use OnceCallback, it probably requires a larger change invloving
changing the client sites of ProtoDatabase.

BUG=722705

Review-Url: https://codereview.chromium.org/2881173003
Cr-Commit-Position: refs/heads/master@{#475750}
Committed:
https://chromium.googlesource.com/chromium/src/+/ca5a950a9da72f942db32e10751f...
==========

[commit-bot: I haz the power, 2017-05-31 02:28:49]

Committed patchset #9 (id:260001) as
https://chromium.googlesource.com/chromium/src/+/ca5a950a9da72f942db32e10751f...