Use glyph index as backup of ExtGID on Mac

Use m_GlyphIndex as backup for m_ExtGID on Mac

When CGFontGetGlyphWithGlyphName returns 0, it means the glyph name
was not recognized. In this case, try using the glyph index to load the
glyph. 

BUG=pdfium:625
Committed: https://pdfium.googlesource.com/pdfium/+/4ee6139e8cfecab9e181115894b26131ad6de09a

[npm, 2016-10-24 21:40:47]

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

[commit-bot: I haz the power, 2016-10-24 21:40:56]

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, 2016-10-24 22:16:34]

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

[commit-bot: I haz the power, 2016-10-24 22:16:34]

Dry run: This issue passed the CQ dry run.

[npm, 2016-10-25 14:55:05]

Description was changed from

==========
Use glyph index as backup of ExtGID on Mac
==========

to

==========
Use m_GlyphIndex as backup for m_ExtGID on Mac

When CGFontGetGlyphWithGlyphName returns 0, it means the glyph name
was not recognized. In this case, try using the glyph index to load the
glyph. 

BUG=pdfium:625
==========

[npm, 2016-10-25 14:55:05]

npm@chromium.org changed reviewers:
+ thestig@chromium.org

[npm, 2016-10-25 14:55:18]

PTAL

[Lei Zhang, 2016-10-25 18:25:05]

lgtm

[npm, 2016-10-25 18:36:44]

The CQ bit was checked by npm@chromium.org

[commit-bot: I haz the power, 2016-10-25 18:36:48]

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, 2016-10-25 18:37:06]

Description was changed from

==========
Use m_GlyphIndex as backup for m_ExtGID on Mac

When CGFontGetGlyphWithGlyphName returns 0, it means the glyph name
was not recognized. In this case, try using the glyph index to load the
glyph. 

BUG=pdfium:625
==========

to

==========
Use m_GlyphIndex as backup for m_ExtGID on Mac

When CGFontGetGlyphWithGlyphName returns 0, it means the glyph name
was not recognized. In this case, try using the glyph index to load the
glyph. 

BUG=pdfium:625

Committed:
https://pdfium.googlesource.com/pdfium/+/4ee6139e8cfecab9e181115894b26131ad6d...
==========

[commit-bot: I haz the power, 2016-10-25 18:37:07]

Committed patchset #1 (id:1) as
https://pdfium.googlesource.com/pdfium/+/4ee6139e8cfecab9e181115894b26131ad6d...