Always include public/include headers for vulkan and just guard src files with SK_VULKAN.

This should allow a client to build a skia library that doesn't use vulkan but still
has all the public headers defined so that they don't have to build two versions of
their code.

Bug: chromium:862144
Change-Id: I0eecbe0bc48123619f217e2cf318eb9a8c77ccb2
Reviewed-on: https://skia-review.googlesource.com/158661
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrDirectContext.cpp b/src/gpu/GrDirectContext.cpp
index 14133cd..59b984c 100644
--- a/src/gpu/GrDirectContext.cpp
+++ b/src/gpu/GrDirectContext.cpp
@@ -147,14 +147,19 @@
     return context;
 }
 
-#ifdef SK_VULKAN
 sk_sp<GrContext> GrContext::MakeVulkan(const GrVkBackendContext& backendContext) {
+#ifdef SK_VULKAN
     GrContextOptions defaultOptions;
     return MakeVulkan(backendContext, defaultOptions);
+#else
+    return nullptr;
+#endif
 }
 
 sk_sp<GrContext> GrContext::MakeVulkan(const GrVkBackendContext& backendContext,
                                        const GrContextOptions& options) {
+#ifdef SK_VULKAN
+    GrContextOptions defaultOptions;
     sk_sp<GrContext> context(new GrDirectContext(kVulkan_GrBackend));
 
     context->fGpu = GrVkGpu::Make(backendContext, options, context.get());
@@ -167,8 +172,10 @@
         return nullptr;
     }
     return context;
-}
+#else
+    return nullptr;
 #endif
+}
 
 #ifdef SK_METAL
 sk_sp<GrContext> GrContext::MakeMetal(void* device, void* queue) {