Gfxbench Manhattan uses depth attachment as texture in the same render
pass, which creates a feedback loop. The layout we are using for this
has kAllShadersPipelineStageFlags even though it only used by fragment
shader. This creates an unnecessary vertex/fragment dependency that
hurts performance on some mobile GPUs. This CL split
DepthStencilReadOnly to DSAttachmentReadAndFragmentShaderRead,
DSAttachmentReadAndAllShadersRead, and DepthStencilAttachmentReadOnly,
so that if it is used by fragment shader, we only barrier against
fragment stage. If not used by any shader, we don't block any shader
stages. To make names consistent, this CL also renames
DepthStencilAttachmentAndFragmentShaderRead to
DSAttachmentWriteAndFragmentShaderRead, renames
DepthStencilAttachmentAndAllShadersRead to
DSAttachmentWriteAndAllShadersRead.

Bug: b/169891513
Change-Id: Iede497e8af028861f9166a32d122f26dc7aa864a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2453599
Commit-Queue: Charlie Lao <cclao@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>