The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9f363d853d714ebd13fb0abb951cddc83451912a

commit 9f363d853d714ebd13fb0abb951cddc83451912a
Author: hayato <hayato@chromium.org>
Date: Fri Apr 15 08:31:09 2016

Fix querySelectorAll for multiple Ids in a shadow tree

One of the code paths in the selector query code looks up IDs in the document scope
instead of the tree-scope for the shadow tree when querying inside a shadow tree.

This CL is separated CL from https://codereview.chromium.org/1883083002

BUG= 603431 

Review URL: https://codereview.chromium.org/1892743002

Cr-Commit-Position: refs/heads/master@{#387561}

[add] https://crrev.com/9f363d853d714ebd13fb0abb951cddc83451912a/third_party/WebKit/LayoutTests/shadow-dom/query-selector.html
[modify] https://crrev.com/9f363d853d714ebd13fb0abb951cddc83451912a/third_party/WebKit/Source/core/dom/SelectorQuery.cpp