Add Vulkan validation layers on Windows

Deploy self-built Vulkan validation layers instead of system installed
one. And it will reuse third_party/angle's Vulkan validation layers if
building with chromium.

Bug: dawn:150
Change-Id: I94e26f7a152fb2a1c39bcb102d60024f4d65eee6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/11120
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

scripts/dawn_features.gni

@@ -45,3 +45,11 @@ declare_args() {
   # compiler, since it is a sub-class of if.
   dawn_enable_cross_reflection = false
 }
+
+# GN does not allow reading a variable defined in the same declare_args().
+# Put them in two separate declare_args() when setting the value of one
+# argument based on another.
+declare_args() {
+  # Uses our built version of Vulkan validation layers
+  dawn_enable_vulkan_validation_layers = dawn_enable_vulkan && is_win
+}

scripts/dawn_overrides_with_defaults.gni

@@ -56,3 +56,7 @@ if (!defined(dawn_spirv_cross_dir)) {
 if (!defined(dawn_spirv_tools_dir)) {
   dawn_spirv_tools_dir = "//third_party/SPIRV-Tools"
 }
+
+if (!defined(dawn_vulkan_validaion_layers_dir)) {
+  dawn_vulkan_validaion_layers_dir = "//third_party/vulkan-validation-layers"
+}