GCC doesn't use the std:: namespace for these methods.

BUG=angle:773

Change-Id: I0d887f103298cdd184b3f7825c5e44363edb9b92
Reviewed-on: https://chromium-review.googlesource.com/232697Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>