Revert of libxml2: linearly optimize XPath expressions.

Revert of libxml2: linearly optimize XPath expressions. (patchset #4 id:60001 of https://codereview.chromium.org/1562133002/ )

Reason for revert:
MSAN failure - use of uninitialized value.

Original issue's description:
> libxml2: linearly optimize XPath expressions.
>
> Some XPath expression nodes keep a back pointer to the last/previous
> expression node for optimization purposes. Such pointers will result
> in repeated work when walking over the expression
> tree/graph, peephole optimizing it. Unacceptable amounts of repeated
> work as the expression tree becomes deeper.
>
> Avoid by marking the expression nodes during the optimization pass.
>
> R=scottmg
> BUG=573768
>
> Committed: https://crrev.com/0b208a502be9d60929be48056dd4213efd998076
> Cr-Commit-Position: refs/heads/master@{#369733}

TBR=scottmg@chromium.org,cpu@chromium.org,thakis@chromium.org,sigbjornf@opera.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=573768
Committed: https://crrev.com/3d68bdb9bd3c12b59b816a65a84741dccb9fa0c1
Cr-Commit-Position: refs/heads/master@{#369806}

[jsbell, 2016-01-15 19:17:41]

Created Revert of libxml2: linearly optimize XPath expressions.

[commit-bot: I haz the power, 2016-01-15 19:19:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1597603002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1597603002/1

[commit-bot: I haz the power, 2016-01-15 19:22:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-15 19:23:22]

Description was changed from

==========
Revert of libxml2: linearly optimize XPath expressions. (patchset #4 id:60001 of
https://codereview.chromium.org/1562133002/ )

Reason for revert:
MSAN failure - use of uninitialized value.

Original issue's description:
> libxml2: linearly optimize XPath expressions.
> 
> Some XPath expression nodes keep a back pointer to the last/previous
> expression node for optimization purposes. Such pointers will result
> in repeated work when walking over the expression
> tree/graph, peephole optimizing it. Unacceptable amounts of repeated
> work as the expression tree becomes deeper.
> 
> Avoid by marking the expression nodes during the optimization pass.
> 
> R=scottmg
> BUG=573768
> 
> Committed: https://crrev.com/0b208a502be9d60929be48056dd4213efd998076
> Cr-Commit-Position: refs/heads/master@{#369733}

TBR=scottmg@chromium.org,cpu@chromium.org,thakis@chromium.org,sigbjornf@opera...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=573768
==========

to

==========
Revert of libxml2: linearly optimize XPath expressions. (patchset #4 id:60001 of
https://codereview.chromium.org/1562133002/ )

Reason for revert:
MSAN failure - use of uninitialized value.

Original issue's description:
> libxml2: linearly optimize XPath expressions.
>
> Some XPath expression nodes keep a back pointer to the last/previous
> expression node for optimization purposes. Such pointers will result
> in repeated work when walking over the expression
> tree/graph, peephole optimizing it. Unacceptable amounts of repeated
> work as the expression tree becomes deeper.
>
> Avoid by marking the expression nodes during the optimization pass.
>
> R=scottmg
> BUG=573768
>
> Committed: https://crrev.com/0b208a502be9d60929be48056dd4213efd998076
> Cr-Commit-Position: refs/heads/master@{#369733}

TBR=scottmg@chromium.org,cpu@chromium.org,thakis@chromium.org,sigbjornf@opera...
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=573768

Committed: https://crrev.com/3d68bdb9bd3c12b59b816a65a84741dccb9fa0c1
Cr-Commit-Position: refs/heads/master@{#369806}
==========

[commit-bot: I haz the power, 2016-01-15 19:23:22]

Patchset 1 (id:??) landed as
https://crrev.com/3d68bdb9bd3c12b59b816a65a84741dccb9fa0c1
Cr-Commit-Position: refs/heads/master@{#369806}

[sof, 2016-01-15 20:44:52]

lgtm