Reland of move enable_vulkan from build/config, and move it to the buildflag_header system. (patchset #1 id:1 of https://codereview.chromium.org/2742263004/ )

Reason for revert:
Relanding since this revert doesn't appear to have helped:
https://build.chromium.org/p/chromium.linux/builders/Linux%20Tests

Original issue's description:
> Revert of Remove enable_vulkan from build/config, and move it to the buildflag_header system. (patchset #8 id:140001 of https://codereview.chromium.org/2744973002/ )
>
> Reason for revert:
> Speculative revert for linux tests failure:
> https://build.chromium.org/p/chromium.linux/builders/Linux%20Tests
>
> Original issue's description:
> > Remove enable_vulkan from build/config, and move it to the buildflag_header system.
> >
> > No intended behavior change.
> >
> > TBR=avi
> > BUG=none
> > CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
> >
> > Review-Url: https://codereview.chromium.org/2744973002
> > Cr-Commit-Position: refs/heads/master@{#456525}
> > Committed: https://chromium.googlesource.com/chromium/src/+/7f118188c140989c8a633c60d531b4c08eef8564
>
> TBR=dyen@chromium.org,danakj@chromium.org,jbauman@chromium.org,avi@chromium.org,piman@chromium.org,thakis@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=none
>
> Review-Url: https://codereview.chromium.org/2742263004
> Cr-Commit-Position: refs/heads/master@{#456562}
> Committed: https://chromium.googlesource.com/chromium/src/+/0192171168e7afc337edc13c150eca4152185cd5

TBR=dyen@chromium.org,danakj@chromium.org,jbauman@chromium.org,avi@chromium.org,piman@chromium.org,thakis@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=none

Review-Url: https://codereview.chromium.org/2746363002
Cr-Commit-Position: refs/heads/master@{#456613}

diff --git a/cc/BUILD.gn b/cc/BUILD.gn
index 183a9f12b..f7991eee 100644
--- a/cc/BUILD.gn
+++ b/cc/BUILD.gn

@@ -2,8 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build/config/ui.gni")
 import("//cc/cc.gni")
+import("//gpu/vulkan/features.gni")
 
 cc_component("cc") {
   sources = [
@@ -533,6 +533,7 @@
     "//gpu/command_buffer/client:gles2_interface",
     "//gpu/ipc:gl_in_process_context",
     "//gpu/skia_bindings:skia_bindings",
+    "//gpu/vulkan:features",
     "//media",
     "//mojo/public/cpp/bindings:struct_traits",
     "//third_party/libyuv",