Simplify the id fast path for non-right most selectors in querySelector.

Simplify the id fast path for non-right most selectors in querySelector.

The id path inside SelectorQuery::findTraverseRootsAndExecute is not actually
reachable for the right most selector since we handle that separately inside
the top level ::execute() call. We also only ever take the fast path when
rootNode.isConnected() (as checked by canUseFastPath) so we can use that too.

By using these two truths inside this code we can simplify what it was doing
and delete a bunch of the code.

BUG=703900
Review-Url: https://codereview.chromium.org/2786763002
Cr-Commit-Position: refs/heads/master@{#460572}
Committed: https://chromium.googlesource.com/chromium/src/+/d3b15e0c4bb54971c3d689537a2b08c91a89238b

[esprehn, 2017-03-29 19:55:15]

The CQ bit was checked by esprehn@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-29 19:56:21]

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

[esprehn, 2017-03-29 19:59:43]

https://codereview.chromium.org/2786763002/diff/1/third_party/WebKit/Source/c...
File third_party/WebKit/Source/core/dom/SelectorQuery.cpp (left):

https://codereview.chromium.org/2786763002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/dom/SelectorQuery.cpp:247: if (selector->match()
== CSSSelector::Id && rootNode.isInTreeScope() &&
We only take the fast path if rootNode.isConnected() is true (inside
canUseFastPath), so we know isInTreeScope() must be true.

https://codereview.chromium.org/2786763002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/dom/SelectorQuery.cpp:253: if (element &&
element->isDescendantOf(&rootNode))
if element was null, then there's no element in this TreeScope with this id, so
the selector cannot match at all, so we can just early return.

https://codereview.chromium.org/2786763002/diff/1/third_party/WebKit/Source/c...
third_party/WebKit/Source/core/dom/SelectorQuery.cpp:257: if
(isRightmostSelector) {
This code was not reachable, id selectors in the right most selector are handled
by the selectorForIdLookup() fast path inside ::execute() that comes before this
function call. I've replaced this path with a DCHECK.

[esprehn, 2017-03-29 20:31:31]

The CQ bit was checked by esprehn@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-29 20:32:47]

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

[esprehn, 2017-03-29 20:38:16]

Description was changed from

==========
Simplify the id fast path for non-right most selectors in querySelector.

BUG=703900
==========

to

==========
Simplify the id fast path for non-right most selectors in querySelector.

The id path inside SelectorQuery::findTraverseRootsAndExecute is not actually
reachable for the right most selector since we handle that separately inside
the top level ::execute() call. We also only ever take the fast path when
rootNode.isConnected() (as checked by canUseFastPath) so we can use that too.

By using these two truths inside this code we can simplify what it was doing
and delete a bunch of the code.

BUG=703900
==========

[esprehn, 2017-03-29 21:41:08]

esprehn@chromium.org changed reviewers:
+ dglazkov@chromium.org, meade@chromium.org, rune@opera.com

[dglazkov, 2017-03-29 22:23:35]

lgtm

[esprehn, 2017-03-29 22:34:31]

The CQ bit was unchecked by esprehn@chromium.org

[esprehn, 2017-03-29 22:34:32]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2017-03-29 22:35:05]

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, 2017-03-29 23:22:50]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1490826872770280,
"parent_rev": "d24a096f2db3e68da5d48df57a75cf643da1e178", "commit_rev":
"d3b15e0c4bb54971c3d689537a2b08c91a89238b"}

[commit-bot: I haz the power, 2017-03-29 23:23:33]

Description was changed from

==========
Simplify the id fast path for non-right most selectors in querySelector.

The id path inside SelectorQuery::findTraverseRootsAndExecute is not actually
reachable for the right most selector since we handle that separately inside
the top level ::execute() call. We also only ever take the fast path when
rootNode.isConnected() (as checked by canUseFastPath) so we can use that too.

By using these two truths inside this code we can simplify what it was doing
and delete a bunch of the code.

BUG=703900
==========

to

==========
Simplify the id fast path for non-right most selectors in querySelector.

The id path inside SelectorQuery::findTraverseRootsAndExecute is not actually
reachable for the right most selector since we handle that separately inside
the top level ::execute() call. We also only ever take the fast path when
rootNode.isConnected() (as checked by canUseFastPath) so we can use that too.

By using these two truths inside this code we can simplify what it was doing
and delete a bunch of the code.

BUG=703900

Review-Url: https://codereview.chromium.org/2786763002
Cr-Commit-Position: refs/heads/master@{#460572}
Committed:
https://chromium.googlesource.com/chromium/src/+/d3b15e0c4bb54971c3d689537a2b...
==========

[commit-bot: I haz the power, 2017-03-29 23:23:36]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/d3b15e0c4bb54971c3d689537a2b...