Perform the loop-exit test when continuing from inside a do-while.

SPIR-V would previously jump to the top of the do-while loop when
encountering a `continue`. This is not correct; it should jump to the
loop-exit test. We don't have any real shaders which test this case, and
it can't be checked from inside Runtime Effects since do-while is not
part of ES2.

Change-Id: Iac58e9e7ad0a94640e6418afea096b19ba50a2df
Bug: skia:11874
Reviewed-by: Ethan Nicholas <>
Commit-Queue: John Stiles <>
6 files changed