Add a new mechanism for watching SVGElement 'href' targets

Add a new mechanism for watching SVGElement 'href' targets

This CL adds a new mechanism for watching elements referenced via 'href'
attributes. It uses IdTargetObserver as the basis adding a callback for
notification.
This is a step away from relying on SVGTreeScopeResources for tracking
of "pending" elements for these use cases. Each element is instead does
its own tracking via the relevant TreeScope. This will eventually mean
that the buildPendingResourcesIfNeeded mechanism can be removed.

SVGTextPathElement and SVGMPathElement are updated to use this new
scheme. Other uses will be replaced in future CLs.

BUG=661598
Review-Url: https://codereview.chromium.org/2737653006
Cr-Commit-Position: refs/heads/master@{#455584}
Committed: https://chromium.googlesource.com/chromium/src/+/43f91d7f998095673e151be50bf17fe1b011f080

[fs, 2017-03-08 16:59:23]

The CQ bit was checked by fs@opera.com to run a CQ dry run

[commit-bot: I haz the power, 2017-03-08 16:59:48]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-08 18:35:10]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-03-08 18:35:12]

Dry run: This issue passed the CQ dry run.

[fs, 2017-03-08 18:59:42]

fs@opera.com changed reviewers:
+ pdr@chromium.org, schenney@chromium.org

[pdr., 2017-03-08 19:04:57]

Looking great, I like the ultimate direction.

LGTM

[fs, 2017-03-08 22:56:38]

The CQ bit was checked by fs@opera.com

[commit-bot: I haz the power, 2017-03-08 22:57:09]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-03-08 23:14:30]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1489013798263130, "parent_rev":
"90de89fc0ee5f555ae43be4bd820db72307f9c5c", "commit_rev":
"43f91d7f998095673e151be50bf17fe1b011f080"}

[commit-bot: I haz the power, 2017-03-08 23:15:11]

Description was changed from

==========
Add a new mechanism for watching SVGElement 'href' targets

This CL adds a new mechanism for watching elements referenced via 'href'
attributes. It uses IdTargetObserver as the basis adding a callback for
notification.
This is a step away from relying on SVGTreeScopeResources for tracking
of "pending" elements for these use cases. Each element is instead does
its own tracking via the relevant TreeScope. This will eventually mean
that the buildPendingResourcesIfNeeded mechanism can be removed.

SVGTextPathElement and SVGMPathElement are updated to use this new
scheme. Other uses will be replaced in future CLs.

BUG=661598
==========

to

==========
Add a new mechanism for watching SVGElement 'href' targets

This CL adds a new mechanism for watching elements referenced via 'href'
attributes. It uses IdTargetObserver as the basis adding a callback for
notification.
This is a step away from relying on SVGTreeScopeResources for tracking
of "pending" elements for these use cases. Each element is instead does
its own tracking via the relevant TreeScope. This will eventually mean
that the buildPendingResourcesIfNeeded mechanism can be removed.

SVGTextPathElement and SVGMPathElement are updated to use this new
scheme. Other uses will be replaced in future CLs.

BUG=661598

Review-Url: https://codereview.chromium.org/2737653006
Cr-Commit-Position: refs/heads/master@{#455584}
Committed:
https://chromium.googlesource.com/chromium/src/+/43f91d7f998095673e151be50bf1...
==========

[commit-bot: I haz the power, 2017-03-08 23:15:12]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/43f91d7f998095673e151be50bf1...