Revert "Revert "Update skia to use ifdefs for Vulkan code instead of dummy header""

This reverts commit fad9e3f54112ea8c8bb6bb72384f47b9759578f5.

Reason for revert: Can't find the error message anymore (?!?) Let's try again shall we

Original change's description:
> Revert "Update skia to use ifdefs for Vulkan code instead of dummy header"
> 
> This reverts commit c0f8e426c59eec6c720b8e1329dcb966cf1b6800.
> 
> Reason for revert: Experiment to see if this will unblock the Android roll
> 
> Original change's description:
> > Update skia to use ifdefs for Vulkan code instead of dummy header
> > 
> > Bug: skia:6721
> > Change-Id: I80a4c9f2acc09c174497f625c50ed12a8bb76505
> > Reviewed-on: https://skia-review.googlesource.com/19547
> > Reviewed-by: Mike Klein <mtklein@google.com>
> > Commit-Queue: Greg Daniel <egdaniel@google.com>
> 
> TBR=egdaniel@google.com,mtklein@google.com,bsalomon@google.com
> 
> Change-Id: Ib51c1672570f2071a17b6fbde692a5174b0358ce
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: skia:6721
> Reviewed-on: https://skia-review.googlesource.com/19724
> Reviewed-by: Robert Phillips <robertphillips@google.com>
> Commit-Queue: Robert Phillips <robertphillips@google.com>

TBR=egdaniel@google.com,mtklein@google.com,bsalomon@google.com,robertphillips@google.com

Change-Id: Iecef7ddcfe31d82938336120a4193525ac6693be
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:6721
Reviewed-on: https://skia-review.googlesource.com/19782
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index bb355c6..e3f87bc 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -55,17 +55,14 @@
   }
 }
 declare_args() {
+  skia_vulkan_headers = ""
   if (skia_use_vulkan) {
+    # When buliding on Android we get the header via the NDK so no need for any extra path.
     if (is_fuchsia) {
       skia_vulkan_headers = "$fuchsia_vulkan_sdk/include"
     } else if (is_linux || is_win) {
       skia_vulkan_headers = "$skia_vulkan_sdk/include"
-    } else {
-      # When buliding on Android we get the header via the NDK
-      skia_vulkan_headers = ""
     }
-  } else {
-    skia_vulkan_headers = "third_party/vulkan"
   }
 }
 
@@ -91,6 +88,10 @@
   "include/utils/mac",
 ]
 
+if (skia_use_vulkan) {
+  skia_public_includes += [ "include/gpu/vk" ]
+}
+
 # Skia public API, generally provided by :skia.
 config("skia_public") {
   include_dirs = skia_public_includes
@@ -748,8 +749,7 @@
     skia_h = "$target_gen_dir/skia.h"
     script = "gn/find_headers.py"
     args = [ rebase_path(skia_h, root_build_dir) ] +
-           rebase_path(skia_public_includes) +
-           [ rebase_path("third_party/vulkan") ]
+           rebase_path(skia_public_includes)
     depfile = "$skia_h.deps"
     outputs = [
       skia_h,