Update pdf.gypi to actually work with Chromium

Recent PDF changes have broken the Chromium Canary making it an excellent time to start using our pdf.gypi in Chromium's skia_library.gypi file. 

This slight modification is required since Chrome doesn't build the SkDocument_PDF.cpp file.

[djsollen, 2013-08-23 20:49:31]

https://codereview.chromium.org/23112031/diff/1/gyp/pdf.gyp
File gyp/pdf.gyp (right):

https://codereview.chromium.org/23112031/diff/1/gyp/pdf.gyp#newcode23
gyp/pdf.gyp:23: '../src/doc/SkDocument_PDF.cpp', # Chromium does use this file
what will it hurt if chromium does build this?

[robertphillips, 2013-08-25 12:04:20]

https://codereview.chromium.org/23112031/diff/1/gyp/pdf.gyp
File gyp/pdf.gyp (right):

https://codereview.chromium.org/23112031/diff/1/gyp/pdf.gyp#newcode23
gyp/pdf.gyp:23: '../src/doc/SkDocument_PDF.cpp', # Chromium does use this file
I don't know but it should probably be intentionally added rather than just
glommed in there.

[djsollen, 2013-08-26 11:19:30]

On 2013/08/25 12:04:20, robertphillips wrote:
> https://codereview.chromium.org/23112031/diff/1/gyp/pdf.gyp
> File gyp/pdf.gyp (right):
> 
> https://codereview.chromium.org/23112031/diff/1/gyp/pdf.gyp#newcode23
> gyp/pdf.gyp:23: '../src/doc/SkDocument_PDF.cpp', # Chromium does use this file
> I don't know but it should probably be intentionally added rather than just
> glommed in there.

[djsollen, 2013-08-26 11:26:05]

So the only files to go into the *.gypi are the ones that chromium needs?  If so
shouldn't we be specific that these *.gypi (core, effects, pdf) are not for all
our sources and just chromium?  For the record, I'm not sure I buy into an
approach where our build system is so centric around one client.

[robertphillips, 2013-08-26 12:52:41]

I'm not sure files in doc belong in the pdf.gypi. Although we blend other gypi
(e.g., core.gypi has files form core, doc, image, pipe, lazy and pathops) I
don't know if that is the clearest approach. effects.gypi only has files from
effects while gpu.gypi has files from gpu & image.

[djsollen, 2013-08-26 13:04:22]

lgtm and we can do the gypi refactoring later

[commit-bot: I haz the power, 2013-08-26 13:15:37]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/robertphillips@google.com/23112031/1

[commit-bot: I haz the power, 2013-08-26 13:37:56]

Retried try job too often on Build-Mac10.7-Clang-x86-Release-Trybot for step(s)
BuildMost
http://173.255.115.253:10117/buildstatus?builder=Build-Mac10.7-Clang-x86-Rele...

[robertphillips, 2013-08-26 13:47:37]

committed as r10916