Use CorrespondingUseElement() in SVGElement::TreeScopeForIdResolution

Use CorrespondingUseElement() in SVGElement::TreeScopeForIdResolution

For elements sourced non-locally, CorrespondingElement() will give the
TreeScope of the document it was sourced from rather than the TreeScope
of the <use> element. Until we are able to resolve references at
ComputedStyle resolution, attempt to use the host of the shadow tree,
i.e the (outermost) <use> element. (This will not work when external
paint servers are supported, or with a paint server defined in the
referenced document.)

BUG=721167
Review-Url: https://codereview.chromium.org/2877973002
Cr-Original-Commit-Position: refs/heads/master@{#471955}
Review-Url: https://codereview.chromium.org/2887433003 .
Cr-Commit-Position: refs/branch-heads/3071@{#576}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/1d80901cae8f06131cce44f0719d93cd580bd3df

[fs, 2017-05-16 06:30:21]

Description was changed from

==========
Use CorrespondingUseElement() in SVGElement::TreeScopeForIdResolution

For elements sourced non-locally, CorrespondingElement() will give the
TreeScope of the document it was sourced from rather than the TreeScope
of the <use> element. Until we are able to resolve references at
ComputedStyle resolution, attempt to use the host of the shadow tree,
i.e the (outermost) <use> element. (This will not work when external
paint servers are supported, or with a paint server defined in the
referenced document.)

BUG=721167

Review-Url: https://codereview.chromium.org/2877973002
Cr-Commit-Position: refs/heads/master@{#471955}
(cherry picked from commit 6d8df7c57b4cc1beb9816b7379d88a48650dd507)
==========

to

==========
Use CorrespondingUseElement() in SVGElement::TreeScopeForIdResolution

For elements sourced non-locally, CorrespondingElement() will give the
TreeScope of the document it was sourced from rather than the TreeScope
of the <use> element. Until we are able to resolve references at
ComputedStyle resolution, attempt to use the host of the shadow tree,
i.e the (outermost) <use> element. (This will not work when external
paint servers are supported, or with a paint server defined in the
referenced document.)

BUG=721167

Review-Url: https://codereview.chromium.org/2877973002
Cr-Original-Commit-Position: refs/heads/master@{#471955}
Review-Url: https://codereview.chromium.org/2887433003 .
Cr-Commit-Position: refs/branch-heads/3071@{#576}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/1d80901cae8f06131cce44f0719d...
==========

[fs, 2017-05-16 06:30:23]

Committed patchset #1 (id:1) manually as
1d80901cae8f06131cce44f0719d93cd580bd3df.