relnote: refactoring the buffering logic in QUIC's stream sequencer.

relnote: refactoring the buffering logic in QUIC's stream sequencer.

Add a wrapper class QuicFrameList for underlying buffered_frames_ list in
QuicStreamSequencer to prepare for future changes of data structure for
buffered_frames_. It shares the same interface with its substitution
StreamSequencerBuffer.

Merge internal change: 104518889

R=rch@chromium.org
BUG=

Committed: https://crrev.com/f160a6ead8049f80e7f63cdf939ba01f436b75f5
Cr-Commit-Position: refs/heads/master@{#354361}

[Ryan Hamilton, 2015-10-15 13:45:22]

lgtm

[Buck, 2015-10-15 21:15:44]

The CQ bit was checked by ckrasic@chromium.org

[Buck, 2015-10-15 21:15:45]

The patchset sent to the CQ was uploaded after l-g-t-m from rch@chromium.org
Link to the patchset: https://codereview.chromium.org/1400293002/#ps120001
(title: "disentangle merge of 104894802")

[commit-bot: I haz the power, 2015-10-15 21:16:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1400293002/120001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1400293002/120001

[commit-bot: I haz the power, 2015-10-15 21:28:09]

Committed patchset #7 (id:120001)

[commit-bot: I haz the power, 2015-10-15 21:29:01]

Patchset 7 (id:??) landed as
https://crrev.com/f160a6ead8049f80e7f63cdf939ba01f436b75f5
Cr-Commit-Position: refs/heads/master@{#354361}