[Cronet] Remove buffer.compact from CronetChunkedOutputStream

[Cronet] Remove buffer.compact from CronetChunkedOutputStream

This CL unifies the buffer manipulation code in CronetChunkedOutputStream to
match the one in CronetFixedOutputStream.

BUG=626653
TBR=kapishnikov@chromium.org
TBR=mef@chromium.org

NOTRY=true
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2133273002
Cr-Commit-Position: refs/heads/master@{#404664}
(cherry picked from commit bf9178a723b6fb899d7b73f2793d532fc4badd66)

[xunjieli, 2016-07-11 18:50:40]

This is to merge the change into M53. I will CQ it once I confirmed that locally
tests are still passing. Thanks.

[xunjieli, 2016-07-11 19:20:01]

The CQ bit was checked by xunjieli@chromium.org

[xunjieli, 2016-07-11 19:20:16]

On 2016/07/11 18:50:40, xunjieli wrote:
> This is to merge the change into M53. I will CQ it once I confirmed that
locally
> tests are still passing. Thanks.

Verified locally that tests are still passing.

[commit-bot: I haz the power, 2016-07-11 19:20:22]

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, 2016-07-11 19:21:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-11 19:21:26]

CQ bit was unchecked.