Enable "-Wshadow-field". This warning verifies we don't give variables names that shadow fields. This is another good warning to enable that Skia requires. This CL also fixes a small number of points in code that used this bad pattern. We have to disable the warning for Glslang for now. Bug: angleproject:4046 Change-Id: I072a686e3023b60cfafa778525fe712ce1fb5a50 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1877476 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>