Preliminary support for Windows manifests in the GN build.

testing/test.gni

Index: testing/test.gni
diff --git a/testing/test.gni b/testing/test.gni
index c99df9036b6d8b636c5bb6912b67a4517475950e..a224ef2918ec5179c94021c1372ffa7ff79f3169 100644
--- a/testing/test.gni
+++ b/testing/test.gni
@@ -203,15 +203,20 @@ template("test") {
         defines = invoker.defines
       }
 
-      # All shared libraries must have the sanitizer deps to properly link in
-      # asan mode (this target will be empty in other cases).
       if (defined(invoker.deps)) {
-        deps = invoker.deps + [ "//build/config/sanitizers:deps" ]
+        deps = invoker.deps
       } else {
-        deps = [
-          "//build/config/sanitizers:deps",
-        ]
+        deps = []
       }
+      deps += [
+        # All shared libraries must have the sanitizer deps to properly link in
+        # asan mode (this target will be empty in other cases).
+        "//build/config/sanitizers:deps",
+
+        # Give tests the default manifest on Windows (a no-op elsewhere).
+        "//build/win:default_exe_manifest",
+      ]
+
       if (defined(invoker.direct_dependent_configs)) {
         direct_dependent_configs = invoker.direct_dependent_configs
       }