For DynamicBuffer avoid calling vkFlushMappedMemoryRanges() or
vkInvalidateMappedMemoryRanges() if the underlying memory is host-
coherent. These calls are not required for host-coherent memory and
may negatively impact performance.

When currently allocating HOST_VISIBLE memory it's possible to also get
HOST_COHERENT memory even though it's not explicitly requested. Because
of this, the change updates the memory allocaiton interfaces through
the stack to pass back the actual allocated memory properties so that
it can be checked to see if it's host-coherent.

Bug: angleproject:2804
Change-Id: Ife95c4b98115b16d16c087dd72dba7d9661fdb46
Reviewed-on: https://chromium-review.googlesource.com/1234276
Commit-Queue: Tobin Ehlis <tobine@google.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>