Refactor GrVkGpuCommandBuffer to handle multiple GrVkCommandBuffers.

This CL is a pre CL to fix some issues where we will need a GpuCB to
internally have multiple commandbuffers that it submits. Because of
this, I need to move the bounds calculations down into the VkGpuCB
since we need to know the bounds for each sub commandbuffer and not
just entire set of commands. In part this is good since GL actually
never needed the calculations so it saves some work there.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3142

Change-Id: Ied918765da3630aa6d87e29ccce6c883b96c4ead
Reviewed-on: https://skia-review.googlesource.com/3142
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
18 files changed