Enable creating protected vulkan backend

This CL allows user to indicate that they have a protected content in
GrVkBackendContext creation which results in protected CommandPool and Queue
usage.

Bug: skia:9016
Change-Id: I6a478d688b6988c2c5e5e98f18f58fb21f9d26ae
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210067
Commit-Queue: Greg Daniel <egdaniel@google.com>
Auto-Submit: Emircan Uysaler <emircan@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/gn/tests.gni b/gn/tests.gni
index ac67998..43523d5 100644
--- a/gn/tests.gni
+++ b/gn/tests.gni
@@ -300,6 +300,7 @@
   "$_tests/VkDrawableTest.cpp",
   "$_tests/VkHardwareBufferTest.cpp",
   "$_tests/VkPriorityExtensionTest.cpp",
+  "$_tests/VkProtectedContextTest.cpp",
   "$_tests/VkWrapTests.cpp",
   "$_tests/VptrTest.cpp",
   "$_tests/WindowRectanglesTest.cpp",