Avoid some string copies in RAPPOR code.

Avoid some string copies in RAPPOR code.

I remembered some RAPPOR tasks being Janky and looked
at sampling profiler data for this code and noticed there
was a lot of string copies. This CL makes some intermediate
parts use StringPiece to avoid some copies. There's still
more copies to go, but this should reduce how many we need.

BUG=none

Committed: https://crrev.com/0037e42c128122bd4ebdf73a135439198f52cdcc
Cr-Commit-Position: refs/heads/master@{#406125}

[Alexei Svitkine (slow), 2016-07-18 21:18:48]

asvitkine@chromium.org changed reviewers:
+ holte@chromium.org

[Steven Holte, 2016-07-18 21:23:55]

lgtm

[Alexei Svitkine (slow), 2016-07-18 21:31:43]

The CQ bit was checked by asvitkine@chromium.org

[commit-bot: I haz the power, 2016-07-18 21:33:16]

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, 2016-07-18 22:38:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-18 22:38:15]

CQ bit was unchecked.

[commit-bot: I haz the power, 2016-07-18 22:39:40]

Description was changed from

==========
Avoid some string copies in RAPPOR code.

I remembered some RAPPOR tasks being Janky and looked
at sampling profiler data for this code and noticed there
was a lot of string copies. This CL makes some intermediate
parts use StringPiece to avoid some copies. There's still
more copies to go, but this should reduce how many we need.

BUG=none
==========

to

==========
Avoid some string copies in RAPPOR code.

I remembered some RAPPOR tasks being Janky and looked
at sampling profiler data for this code and noticed there
was a lot of string copies. This CL makes some intermediate
parts use StringPiece to avoid some copies. There's still
more copies to go, but this should reduce how many we need.

BUG=none

Committed: https://crrev.com/0037e42c128122bd4ebdf73a135439198f52cdcc
Cr-Commit-Position: refs/heads/master@{#406125}
==========

[commit-bot: I haz the power, 2016-07-18 22:39:41]

Patchset 1 (id:??) landed as
https://crrev.com/0037e42c128122bd4ebdf73a135439198f52cdcc
Cr-Commit-Position: refs/heads/master@{#406125}