Shader: Initialize mMaxComputeSharedMemory Uninitalized values are causing retrace failures. mMaxComputeSharedMemory is otherwise only set when the shader is compiled. Test: retrace_restricted_traces.py Bug: angleproject:7815 Change-Id: I9884ac3c8550775d435d6fa7b11d7aebc63c14d5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4026669 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Gert Wollny <gert.wollny@collabora.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>