commit bdf17920ad6a1d02c97159fb0e986eaf2c7fc30f
author Takayoshi Kochi <kochi@chromium.org> Thu Oct 26 23:42:28 2017
committer Commit Bot <commit-bot@chromium.org> Thu Oct 26 23:42:28 2017
tree ba941b5edad2661d4b2463b83cb07b88c94e2a83
parent 2abf4ceed0bd8f362152dd59179a5a1f6686c260

Disable multiple shadow roots

As the first step of removing multiple shadow roots, disable creation of
a shadow root (via Element.createShadowRoot() API) on elements that
already have a shadow root.
Also remove ShadowRoot.olderShadowRoot attribute.

This CL removes the minimal code of the API surface.
We will remove the implementation in later CLs.

For layout tests, test files that depend on multiple shadow roots are
removed, but if a test file contains several tests and only some of
them use multiple shadow roots, the rest are kept.

Found 3 unit tests in editing also depended on multiple shadow roots
and 2 of them are removed, 1 was not really using multiple shadow roots
and modified to use single shadow root.

Intent to remove:
https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/JjtmigNE28M/xGFu3CDLBAAJ

Bug: 489947
Change-Id: I69d64c5a52f907bea4166025bcd18072338abf2e
Reviewed-on: https://chromium-review.googlesource.com/732811
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Reviewed-by: Hayato Ito <hayato@chromium.org>
Commit-Queue: Takayoshi Kochi <kochi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512017}