Vulkan: Add build toggle for validation layers.

We want to be able to build without validation layers to
make it easier to use in other environments (e.g. Android)
When angle_enable_vulkan is true and
angle_enable_vulkan_validation_layers is true, build the
Vulkan validation layers.

Bug: angleproject:2489

Change-Id: I266ad8f757c5992021f249217f2be58f0148fcbf
Reviewed-on: https://chromium-review.googlesource.com/1005558
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 8729021..4b17f38 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -422,21 +422,27 @@
     public_deps = [
       "$angle_root/third_party/vulkan-validation-layers:vulkan_headers",
     ]
-    data_deps = [
-      "$angle_root/third_party/vulkan-validation-layers:vulkan_validation_layers",
-    ]
     public_configs = [
       "$angle_root/third_party/glslang:glslang_config",
       "$angle_root/third_party/vulkan-validation-layers:vulkan_config",
     ]
+    data_deps = [ ]
     if (!is_android) {
       deps += [ "$angle_root/third_party/vulkan-validation-layers:libvulkan" ]
-      data_deps += [
-        "$angle_root/third_party/vulkan-validation-layers:vulkan_gen_json_files",
-        "$angle_root/third_party/vulkan-validation-layers:VkICD_mock_icd",
-      ]
+      data_deps += [ "$angle_root/third_party/vulkan-validation-layers:VkICD_mock_icd" ]
       public_configs += [ "$angle_root/third_party/vulkan-validation-layers:vulkan_loader_config" ]
     }
+
+    if (angle_enable_vulkan_validation_layers) {
+      data_deps += [
+        "$angle_root/third_party/vulkan-validation-layers:vulkan_validation_layers",
+      ]
+      if (!is_android) {
+        data_deps += [
+          "$angle_root/third_party/vulkan-validation-layers:vulkan_gen_json_files",
+        ]
+      }
+    }
   }
 }
 
diff --git a/gni/angle.gni b/gni/angle.gni
index 2390949..e3fe971 100644
--- a/gni/angle.gni
+++ b/gni/angle.gni
@@ -50,6 +50,7 @@
 declare_args() {
   angle_enable_gl_null = angle_enable_gl
   angle_enable_hlsl = angle_enable_d3d9 || angle_enable_d3d11
+  angle_enable_vulkan_validation_layers = angle_enable_vulkan
 }
 
 if (is_win) {