Vulkan: Ensure onFramebufferBoundary is called for offscreen There is peak memory regression observed from crrev.com/c/6022549. What I suspect happening is that for offscreen or single buffered case, glFlush/glFinish is called but bail out because it already submitted or deferred. So we end up not calling onFramebufferBoundary(). This CL ensures we always call onFramebufferBoundary from these two functions for single buffer or offscreen. Also fixed a bug when onSharedPresentContextFlush is called we may end up calling onFramebufferBoundary. To make API names consistent, existing flushImpl() is renamed to flushAndSubmitCommands() and a new flushIMpl is added to wrap around most logic inside flush(). Bug: angleproject:372268711 Change-Id: I54eed8a81f4153d52ab962f213cacc87a73b89ac Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6037491 Reviewed-by: Yuxin Hu <yuxinhu@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Charlie Lao <cclao@google.com>