Make more services' public interfaces flexible wrt location in repo.

mojo/services/gpu/public/interfaces/BUILD.gn

Index: mojo/services/gpu/public/interfaces/BUILD.gn
diff --git a/mojo/services/gpu/public/interfaces/BUILD.gn b/mojo/services/gpu/public/interfaces/BUILD.gn
index e1b73347ea00798e6f70978f2c08a35cf38a95b8..52723ac2f15e0196cfe54cd60ab0967659784c1c 100644
--- a/mojo/services/gpu/public/interfaces/BUILD.gn
+++ b/mojo/services/gpu/public/interfaces/BUILD.gn
@@ -13,7 +13,9 @@ mojom("interfaces") {
     "viewport_parameter_listener.mojom",
   ]
 
+  import_dirs = [ get_path_info("../../../", "abspath") ]
+
   deps = [
-    "//mojo/services/geometry/public/interfaces",
+    "../../../geometry/public/interfaces",
   ]
 }