Merge to XFA: Fix a #include in fpdf_page_func.cpp.

Not sure why building with gyp was working despite the missing '../' but
it wasn't working in stricter build systems.

TBR=dml@google.com

Review URL: https://codereview.chromium.org/1321293003.

(cherry picked from commit fa31d9630aadfe101d3b35e26ce0fc926ec1505b)

Review URL: https://codereview.chromium.org/1345313003 .
2 files changed