Add a vulkan demo for testing and debugging gpu vulkan code with skia

Bug: 866914
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: Ib5c6351cbad98221447e5218e54e4feeefb8e692
Reviewed-on: https://chromium-review.googlesource.com/1184968
Reviewed-by: Victor Miura <vmiura@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586109}

diff --git a/BUILD.gn b/BUILD.gn
index 8f2f9af..7e27afe 100644
--- a/BUILD.gn
+++ b/BUILD.gn

@@ -25,6 +25,7 @@
 import("//ui/ozone/ozone.gni")
 import("//v8/gni/v8.gni")
 import("//v8/snapshot_toolchain.gni")
+import("//gpu/vulkan/features.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
@@ -739,6 +740,10 @@
       "//webrunner:webrunner_unittests",
     ]
   }
+
+  if (enable_vulkan) {
+    deps += [ "//gpu/vulkan/demo" ]
+  }
 }
 
 if (is_fuchsia) {