Use bundled freetype for tests.

Use bundled freetype for the pdfium_test binary.

But use platform freetype for library itself according to the rules
for the platform.

This should greatly reduce per-platform diffs in the corpus tests, but
requires that the corpus be rolled at the same time.

When this rolls into chromium, its src/BUILD.gn will need to be updated
to say third_party:fx_freetype instead of third_party:freetype.

R=jam@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/22955d987b30056d787d5eeb1a8ac8a1277bf5e0

[Tom Sepez, 2015-07-30 00:23:49]

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

[Tom Sepez, 2015-07-30 15:50:14]

tsepez@chromium.org changed reviewers:
+ jam@chromium.org

[Tom Sepez, 2015-07-30 15:51:24]

jam@, for review.  The idea is that we build freetype, but give it a different
name so that -lfreetype will never resolve against it, and then explicitly
include it in the test program only.  Does this break stuff?  Thanks heaps!

[jam, 2015-07-30 17:18:03]

lgtm

https://codereview.chromium.org/1267493005/diff/20001/samples/samples.gyp
File samples/samples.gyp (right):

https://codereview.chromium.org/1267493005/diff/20001/samples/samples.gyp#new...
samples/samples.gyp:27: # of results across platforms.
please copy this comment to the build.gn too so that we have it when the gyp
file is deleted

[Tom Sepez, 2015-07-30 17:21:48]

On 2015/07/30 17:18:03, jam wrote:
> lgtm
> 
> https://codereview.chromium.org/1267493005/diff/20001/samples/samples.gyp
> File samples/samples.gyp (right):
> 
>
https://codereview.chromium.org/1267493005/diff/20001/samples/samples.gyp#new...
> samples/samples.gyp:27: # of results across platforms.
> please copy this comment to the build.gn too so that we have it when the gyp
> file is deleted
Done.

[Tom Sepez, 2015-07-30 17:29:23]

Committed patchset #6 (id:100001) manually as
22955d987b30056d787d5eeb1a8ac8a1277bf5e0 (presubmit successful).