Use the right TextRun length when checking for surrogate pairs

Use the right TextRun length when checking for surrogate pairs

The isValidSurrogatePair helper in LayoutSVGInlineText.cpp operates on a
TextRun and an index, and checks if the character at the index is part
of a valid surrogate pair.
To check the trailing character, the next index is checked against the
length of the TextRun (to see if the character exists).
The TextRun used is a "sub run" of the entire text node, which means
that the operator[] implementation expects accesses to be within the sub
run rather than the "full run".
Since this function is always used for runs that are sub runs, it should
use TextRun::length() rather than TextRun::charactersLength() to stay
consistent with the iteration and the code using it.

BUG=610641
Committed: https://crrev.com/7dabd875312333379d052e609cc9aad621de1754
Cr-Commit-Position: refs/heads/master@{#392880}

[fs, 2016-05-10 15:31:11]

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

[Stephen Chennney, 2016-05-10 15:56:44]

lgtm with a test request.

Can you still make the test crash (with unchanged code) if you add the output
"You should see PASS followed by some [what do you call them] characters".

Future developers might wonder if the extra apparently junk characters are
deliberate.

Failing that, please add a comment to the test file.

[fs, 2016-05-11 07:44:00]

On 2016/05/10 at 15:56:44, schenney wrote:
> lgtm with a test request.
> 
> Can you still make the test crash (with unchanged code) if you add the output
"You should see PASS followed by some [what do you call them] characters".

Sure, that should be unproblematic. Tweaked the trailing char too (needs to be
something RTL/differing directionality.)

[fs, 2016-05-11 08:42:09]

The CQ bit was checked by fs@opera.com

[fs, 2016-05-11 08:42:10]

The patchset sent to the CQ was uploaded after l-g-t-m from
schenney@chromium.org
Link to the patchset: https://codereview.chromium.org/1961953004/#ps20001
(title: "Tweak test")

[commit-bot: I haz the power, 2016-05-11 08:42:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1961953004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1961953004/20001

[commit-bot: I haz the power, 2016-05-11 08:46:15]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-05-11 08:47:34]

Description was changed from

==========
Use the right TextRun length when checking for surrogate pairs

The isValidSurrogatePair helper in LayoutSVGInlineText.cpp operates on a
TextRun and an index, and checks if the character at the index is part
of a valid surrogate pair.
To check the trailing character, the next index is checked against the
length of the TextRun (to see if the character exists).
The TextRun used is a "sub run" of the entire text node, which means
that the operator[] implementation expects accesses to be within the sub
run rather than the "full run".
Since this function is always used for runs that are sub runs, it should
use TextRun::length() rather than TextRun::charactersLength() to stay
consistent with the iteration and the code using it.

BUG=610641
==========

to

==========
Use the right TextRun length when checking for surrogate pairs

The isValidSurrogatePair helper in LayoutSVGInlineText.cpp operates on a
TextRun and an index, and checks if the character at the index is part
of a valid surrogate pair.
To check the trailing character, the next index is checked against the
length of the TextRun (to see if the character exists).
The TextRun used is a "sub run" of the entire text node, which means
that the operator[] implementation expects accesses to be within the sub
run rather than the "full run".
Since this function is always used for runs that are sub runs, it should
use TextRun::length() rather than TextRun::charactersLength() to stay
consistent with the iteration and the code using it.

BUG=610641

Committed: https://crrev.com/7dabd875312333379d052e609cc9aad621de1754
Cr-Commit-Position: refs/heads/master@{#392880}
==========

[commit-bot: I haz the power, 2016-05-11 08:47:35]

Patchset 2 (id:??) landed as
https://crrev.com/7dabd875312333379d052e609cc9aad621de1754
Cr-Commit-Position: refs/heads/master@{#392880}