[m63 merge] Fix OOB Write in QuicStreamSequencerBuffer::OnStreamData

BUG=778505
TBR=rch@chromium.org

(cherry picked from commit a96567f02a0881561c964e5c11afe9c1af17a5f7)

Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I1dfd1d26a2c7ee8fe047f7fe6e4ac2e9b97efa52
Reviewed-on: https://chromium-review.googlesource.com/748282
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Zhongyi Shi <zhongyi@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#513144}
Reviewed-on: https://chromium-review.googlesource.com/755001
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/branch-heads/3239@{#390}
Cr-Branched-From: adb61db19020ed8ecee5e91b1a0ea4c924ae2988-refs/heads/master@{#508578}
2 files changed