Reland of Allow overriding GN build flags

Reland of Allow overriding GN build flags

This reverts commit 038bf0b129e56212a6de0989dca1ae023bb17c5d.

In order to enable XFA from GN builds we need to be able to override
pdf_enable_xfa. To do this a build_overrides/pdfium.gni file needs to be created
in Chrome. To use that, //pdfium.gni reads the override values and sets them
into the defined arguments. We have to create a build_overrides/pdfium.gni file
in PDFium that sets the default overrides for PDFium builds.

BUG=chromium:62400
Committed: https://pdfium.googlesource.com/pdfium/+/fd670fdef8984fd7f8824b17d8fcf52fdec9aacc

[dsinclair, 2016-05-02 18:44:54]

dsinclair@chromium.org changed reviewers:
+ dpranke@chromium.org

[dsinclair, 2016-05-02 18:44:54]

PTAL.

I think this is closer to what the mac overrides are doing? (The Chrome change
is: https://codereview.chromium.org/1937273002/)

[Dirk Pranke, 2016-05-02 23:58:48]

lgtm

[dsinclair, 2016-05-03 13:13:55]

The CQ bit was checked by dsinclair@chromium.org

[commit-bot: I haz the power, 2016-05-03 13:13:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1936313002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1936313002/1

[commit-bot: I haz the power, 2016-05-03 13:14:39]

Description was changed from

==========
Reland of Allow overriding GN build flags

This reverts commit 038bf0b129e56212a6de0989dca1ae023bb17c5d.

In order to enable XFA from GN builds we need to be able to override
pdf_enable_xfa. To do this a build_overrides/pdfium.gni file needs to be created
in Chrome. To use that, //pdfium.gni reads the override values and sets them
into the defined arguments. We have to create a build_overrides/pdfium.gni file
in PDFium that sets the default overrides for PDFium builds.

BUG=chromium:62400
==========

to

==========
Reland of Allow overriding GN build flags

This reverts commit 038bf0b129e56212a6de0989dca1ae023bb17c5d.

In order to enable XFA from GN builds we need to be able to override
pdf_enable_xfa. To do this a build_overrides/pdfium.gni file needs to be created
in Chrome. To use that, //pdfium.gni reads the override values and sets them
into the defined arguments. We have to create a build_overrides/pdfium.gni file
in PDFium that sets the default overrides for PDFium builds.

BUG=chromium:62400

Committed:
https://pdfium.googlesource.com/pdfium/+/fd670fdef8984fd7f8824b17d8fcf52fdec9...
==========

[commit-bot: I haz the power, 2016-05-03 13:14:40]

Committed patchset #1 (id:1) as
https://pdfium.googlesource.com/pdfium/+/fd670fdef8984fd7f8824b17d8fcf52fdec9...