Split third_party/BUILD.gn in per-project files.

Bug: chromium:1064305

Change-Id: I6fc2da97e20865b62ff34a9d1c3f42120ac90348
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/19202
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>

src/common/BUILD.gn

@@ -148,7 +148,7 @@ if (is_win || is_linux || is_mac || is_fuchsia || is_android) {
     ]
     if (dawn_enable_vulkan) {
       public_deps = [
-        "../../third_party:vulkan_headers",
+        "${dawn_root}/third_party/khronos:vulkan_headers",
       ]
     }
     if (is_android) {

src/dawn_native/BUILD.gn

@@ -397,7 +397,7 @@ source_set("dawn_native_sources") {
   if (dawn_enable_opengl) {
     public_deps += [
       ":dawn_native_opengl_loader_gen",
-      "${dawn_root}/third_party:khronos_platform",
+      "${dawn_root}/third_party/khronos:khronos_platform",
     ]
     sources += get_target_outputs(":dawn_native_opengl_loader_gen")
     sources += [
@@ -447,7 +447,7 @@ source_set("dawn_native_sources") {
   }
 
   if (dawn_enable_vulkan) {
-    public_deps += [ "${dawn_root}/third_party:vulkan_headers" ]
+    public_deps += [ "${dawn_root}/third_party/khronos:vulkan_headers" ]
     sources += [
       "vulkan/AdapterVk.cpp",
       "vulkan/AdapterVk.h",

src/tests/BUILD.gn

@@ -328,7 +328,7 @@ source_set("dawn_white_box_tests_sources") {
   ]
 
   if (dawn_enable_vulkan) {
-    deps += [ "${dawn_root}/third_party:vulkan_headers" ]
+    deps += [ "${dawn_root}/third_party/khronos:vulkan_headers" ]
 
     if (is_chromeos) {
       sources += [ "white_box/VulkanImageWrappingTestsDmaBuf.cpp" ]

src/utils/BUILD.gn

@@ -26,7 +26,7 @@ import("${dawn_root}/scripts/dawn_features.gni")
 if (dawn_supports_glfw_for_windowing) {
   group("dawn_glfw") {
     public_deps = [
-      "${dawn_root}/third_party:glfw",
+      "${dawn_root}/third_party/gn/glfw",
     ]
   }
 } else if (is_fuchsia) {