Strip null characters from the shader source when building translated source. Some shaders had trailing null characters that caused the resulting translated source string to not output correctly. BUG=angleproject:1144 Change-Id: I7cd725ee54c9e934fd3cc511de9c2a3c34ac3eec Reviewed-on: https://chromium-review.googlesource.com/461272 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>