FrameCapture: Don't capture trailing zeros in shader strings. This prevents C build errors like the following when applications provide incorrect shader string lengths: error: null character(s) preserved in string literal Bug: angleproject:7402 Change-Id: Iac7bab58533d152c4b6ed525f0cbcbcb8a7c35ad Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4020417 Commit-Queue: Cody Northrop <cnorthrop@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com>