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The vulkan.hpp is included in the upstream Khronos vulkan headers
package. It is a vulkan c++ binding generated from vulkan registry.
It is implemented with c++ template in a single header file.

This change updates gpu::VulkanFunctionPointers to make it compatible
with vulkan.hpp, and adds vulkan_cxx.h which setups several necessary
macros before including <vulkan/vulkan.hpp>. So any code wants to use
vulkan c++ binding just needs to include vulkan_cxx.h.

This change also adds a test for the vulkan c++ binding.

Change-Id: I74c7003008082686984b559c729bdecac1b08efd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2198140
Commit-Queue: Peng Huang <penghuang@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770361}