Added the Vulkan Context Provider implementation.

gpu/vulkan/vulkan_implementation.cc

Index: gpu/vulkan/vulkan_implementation.cc
diff --git a/gpu/vulkan/vulkan_implementation.cc b/gpu/vulkan/vulkan_implementation.cc
index db6a3d52de815d9a5240c4dcc2e80c5f069f45c4..e363c95a1df52e7631e6c925d488376b14618155 100644
--- a/gpu/vulkan/vulkan_implementation.cc
+++ b/gpu/vulkan/vulkan_implementation.cc
@@ -184,6 +184,11 @@ bool InitializeVulkan() {
   return vulkan_instance->valid;
 }
 
+bool VulkanSupported() {
+  DCHECK(vulkan_instance);
+  return vulkan_instance->valid;
+}
+
 VkInstance GetVulkanInstance() {
   DCHECK(vulkan_instance);
   DCHECK(vulkan_instance->valid);