Revert "Let client pass in full extension to GrVkBackendContext."

This reverts commit 45c9dab4c3ec43cedb28d1b8c08e166fe0c2e767.

Reason for revert: fucshia uses GrVkBackendContext. Need to revert earlier changes

Original change's description:
> Let client pass in full extension to GrVkBackendContext.
> 
> Bug: skia:
> Change-Id: I772ab4ccbca0f4f7e7d429d6c421b07d97f0606f
> Reviewed-on: https://skia-review.googlesource.com/131880
> Reviewed-by: Jim Van Verth <jvanverth@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,jvanverth@google.com,bsalomon@google.com

Change-Id: I1a765ff406c83cb234c3614b804fbed677d5a382
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/137901
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/tools/sk_app/VulkanWindowContext.cpp b/tools/sk_app/VulkanWindowContext.cpp
index d038c97..8e0749e 100644
--- a/tools/sk_app/VulkanWindowContext.cpp
+++ b/tools/sk_app/VulkanWindowContext.cpp
@@ -12,7 +12,6 @@
 #include "SkSurface.h"
 #include "VulkanWindowContext.h"
 
-#include "vk/GrVkExtensions.h"
 #include "vk/GrVkImage.h"
 #include "vk/GrVkUtil.h"
 #include "vk/GrVkTypes.h"
@@ -57,8 +56,8 @@
         return;
     }
 
-    if (!backendContext.fInterface->fExtensions.hasExtension(VK_KHR_SURFACE_EXTENSION_NAME) ||
-        !backendContext.fInterface->fExtensions.hasExtension(VK_KHR_SWAPCHAIN_EXTENSION_NAME)) {
+    if (!(backendContext.fExtensions & kKHR_surface_GrVkExtensionFlag) ||
+        !(backendContext.fExtensions & kKHR_swapchain_GrVkExtensionFlag)) {
         return;
     }