Add ANGLE VK repo build overrides

Updating ANGLE to use integrated BUILD.gn files from the Vulkan Loader,
Headers, Tools, and ValidationLayers repos. Need to add these build
overrides files to Chromium as well.

Bug: angleproject:3320
Change-Id: I4306f3383f06eb4a79d4331717445621a16a5331
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610488
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Tobin Ehlis <tobine@google.com>
Auto-Submit: Tobin Ehlis <tobine@google.com>
Cr-Commit-Position: refs/heads/master@{#663215}

build_overrides/vulkan_common.gni

@@ -0,0 +1,10 @@
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//third_party/angle/gni/angle.gni")
+
+vulkan_headers_dir = "//third_party/angle/third_party/vulkan-headers/src"
+
+vulkan_data_subdir = angle_data_dir
+vulkan_gen_subdir = "angle/vulkan"

build_overrides/vulkan_loader.gni

@@ -0,0 +1,11 @@
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build_overrides/vulkan_common.gni")
+
+vulkan_loader_extra_defines = [
+  "ANGLE_VK_DATA_DIR=\"$angle_data_dir\"",
+  "ANGLE_VK_ICD_JSON=\"$angle_data_dir/VkICD_mock_icd.json\"",
+]
+vulkan_loader_shared = angle_shared_libvulkan

build_overrides/vulkan_tools.gni

@@ -0,0 +1,5 @@
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build_overrides/vulkan_common.gni")

build_overrides/vulkan_validation_layers.gni

@@ -0,0 +1,8 @@
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build_overrides/vulkan_common.gni")
+
+vvl_spirv_tools_dir = "//third_party/SPIRV-Tools/src"
+vvl_glslang_dir = "//third_party/glslang/src"