Add an option to unfold short circuiting in AST.

We replace "a || b" with "a ? true : b",
"a && b" with "a ? b : false".

This is to work around short circuiting bug in Mac drivers.

ANGLEBUG=482
TEST=webgl conformance tests
R=alokp@chromium.org, kbr@chromium.org

Review URL: https://codereview.appspot.com/14529048
9 files changed