Enable XFA-Forms for the PDFium plugin.
Enable XFA-Forms for the PDFium plugin.

This is a change to gather stability, performance, and size
data and will be rolled back by 2016-03-15.

This is the gyp portion of the change; the GN variables
controlling the same things currently reside in the pdfium
product itsef.

Review URL: https://codereview.chromium.org/1761673002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#379622}

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