Avoid merging SharedBuffer segments in TextResource::decodedText

Avoid merging SharedBuffer segments in TextResource::decodedText

Before this CL, TextResource could end up triggering costly SharedBuffer::mergeSegmentsIntoBuffer.
This CL removes its call path by using progressive decoding.

BUG=540988
Committed: https://crrev.com/cc4b7c65d7a702419f5a1f71057b3d3e6cb34d5b
Cr-Commit-Position: refs/heads/master@{#358275}

[kouhei (in TOK), 2015-11-06 02:20:30]

kouhei@chromium.org changed reviewers:
+ japhet@chromium.org, tasak@google.com, tzik@chromium.org

[kouhei (in TOK), 2015-11-06 02:20:30]

PTAL. I'll follow up with performance impact measurements result.

[tzik, 2015-11-06 05:19:13]

lgtm

[kouhei (in TOK), 2015-11-06 05:50:31]

Description was changed from

==========
Avoid merging SharedBuffer segments in TextResource::decodedText

BUG=540988
==========

to

==========
Avoid merging SharedBuffer segments in TextResource::decodedText

Before this CL, TextResource could end up triggering costly
SharedBuffer::mergeSegmentsIntoBuffer.
This CL removes its call path by using progressive decoding.

BUG=540988
==========

[kouhei (in TOK), 2015-11-06 05:50:36]

The CQ bit was checked by kouhei@chromium.org

[commit-bot: I haz the power, 2015-11-06 05:50:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1431863004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1431863004/1

[commit-bot: I haz the power, 2015-11-06 06:55:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-06 06:55:57]

Patchset 1 (id:??) landed as
https://crrev.com/cc4b7c65d7a702419f5a1f71057b3d3e6cb34d5b
Cr-Commit-Position: refs/heads/master@{#358275}