If we are transition between different kind of shaderReadOnly, there is
no actual layout change or accessType change. Instead of always insert a
barrier, this will track what shaderStage has made read access and only
insert barrier if the read is from new shader stage. The barrier
inserted will be always from last non-ShaderReadOnly transition. There
is no read to read barrier generated.

Bug: angleproject:4550
Change-Id: I4aeb7d4bddf2d072b60839f98e7af1aa23f977b5
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2204480
Commit-Queue: Charlie Lao <cclao@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>