1. Request a GLES3.0 context
2. Create 2 uniform buffers to be used in the new test case
3. Increase the size of the viewport
4. Add a new test case where we issue draw and buffer
   copy commands. The expectation is that the draw to
   FBO and the copy between the 2 buffers happen in
   parallel.

Bug: angleproject:4633
Test: angle_perftest --gtest_filter=VulkanBarriersPerfBenchmark.Run/vulkan_buffer_copy
Change-Id: I3c5d287c05451f77053962371a96e2de6a8ea00d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2215139
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>