Disable runtime feature CompositeOpaqueFixedPosition

The feature caused performance regression on low dpi devices when a
fix positioned element contains too many children.

Temporarily disble it to unblock Stable release. Will address it through
https://crbug.com/816937.

Bug: 814673
Change-Id: I6f0fea7d6b61f572b4d8da4e54c34d63cc5bc2f1
Reviewed-on: https://chromium-review.googlesource.com/939585
Commit-Queue: Yi Gu <yigu@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#539552}(cherry picked from commit fc95fed8a9e4cadd5842241b0bb93a9991ff0021)
Reviewed-on: https://chromium-review.googlesource.com/939653
Reviewed-by: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/branch-heads/3325@{#612}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
2 files changed