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Three UMA histograms are added to record whether the GPU supports these Vulkan extensions
GPU.VulkanExtSuport.VK_KHR_external_memory_win32,
GPU.VulkanExtSuport.VK_KHR_external_semaphore_win32,
GPU.VulkanExtSuport.VK_KHR_win32_keyed_mutex

BUG=775983
TEST=manual,Chrome://histograms
R=zmo@chromium.org

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I851d262e158c3757ecba74f98f3cc6ac79213a47
Reviewed-on: https://chromium-review.googlesource.com/1025030Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Maggie Chen <magchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554840}