Fix bug in locateSingleElement

Fix bug in locateSingleElement

This bug probably did not show up much because the conditions that
cause the bug also cause unimplemented interface method warnings.

There is a degradation in code quality in mixin method bodies which I will address later.

This bug is unrelated to the recent removal of the 'mask' parameter of locateSingleElement.

R=sigmund@google.com

Committed: https://github.com/dart-lang/sdk/commit/f404301ec3cba3f14afbb4327ea76f07d9830275

[sra1, 2016-08-26 22:24:33]

Description was changed from

==========
Fix bug in locateSingleElement

This bug probably did not show up much because the conditions that
cause the bug also cause unimplemented interface method warnings.
==========

to

==========
Fix bug in locateSingleElement

This bug probably did not show up much because the conditions that
cause the bug also cause unimplemented interface method warnings.

There is a degradation in code quality in mixin method bodies which I will
address later.

This bug is unrelated to the recent removal of the 'mask' parameter of
locateSingleElement.
==========

[sra1, 2016-08-26 22:24:33]

sra@google.com changed reviewers:
+ sigmund@google.com

[Siggi Cherem (dart-lang), 2016-08-26 22:42:28]

lgtm!

[sra1, 2016-08-26 22:52:23]

Description was changed from

==========
Fix bug in locateSingleElement

This bug probably did not show up much because the conditions that
cause the bug also cause unimplemented interface method warnings.

There is a degradation in code quality in mixin method bodies which I will
address later.

This bug is unrelated to the recent removal of the 'mask' parameter of
locateSingleElement.
==========

to

==========
Fix bug in locateSingleElement

This bug probably did not show up much because the conditions that
cause the bug also cause unimplemented interface method warnings.

There is a degradation in code quality in mixin method bodies which I will
address later.

This bug is unrelated to the recent removal of the 'mask' parameter of
locateSingleElement.

R=sigmund@google.com

Committed:
https://github.com/dart-lang/sdk/commit/f404301ec3cba3f14afbb4327ea76f07d9830275
==========

[sra1, 2016-08-26 22:52:24]

Committed patchset #1 (id:1) manually as
f404301ec3cba3f14afbb4327ea76f07d9830275 (presubmit successful).