Privately include our version of vulkan header file in all our src files.

This should allow clients to include Skia and their vulkan files in any
order. However, it does require that when clients are building their
files that include skia with vulkan, they must have vulkan/vulkan_core.h
on their include path somewhere.

Bug: skia:
Change-Id: I969db396c92127be7c8df754926d175f38b8aafa
Reviewed-on: https://skia-review.googlesource.com/c/172147
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/tests/VkDrawableTest.cpp b/tests/VkDrawableTest.cpp
index ff24708..d9aa8b6 100644
--- a/tests/VkDrawableTest.cpp
+++ b/tests/VkDrawableTest.cpp
@@ -11,6 +11,8 @@
 
 #if SK_SUPPORT_GPU && defined(SK_VULKAN)
 
+#include "vk/GrVkVulkan.h"
+
 #include "GrBackendDrawableInfo.h"
 #include "GrContextFactory.h"
 #include "GrContextPriv.h"