Revert "Leak per-isolate data in pdfium"

This reverts commit 3e144b8c23d7c52ed36329e87f0cb01f38ec1ed7.

This may be causing the failures seen in crbug.com/537799.

BUG=537799

Review URL: https://codereview.chromium.org/1382433003 .
1 file changed