Revert of Un-nest configs in GN files.

third_party/libusb/BUILD.gn

Index: third_party/libusb/BUILD.gn
diff --git a/third_party/libusb/BUILD.gn b/third_party/libusb/BUILD.gn
index 82aeabd3790b918739d20f690143322320ec31cc..cce639ea327da46bc41dc93d6468770a284f4bd0 100644
--- a/third_party/libusb/BUILD.gn
+++ b/third_party/libusb/BUILD.gn
@@ -8,17 +8,6 @@
 
 config("libusb_config") {
   include_dirs = [ "src/libusb" ]
-}
-
-config("libusb_warnings") {
-  visibility = [ ":*" ]
-  if (is_clang) {
-    # guid_eq in windows_usb.c is unused.
-    cflags = [ "-Wno-unused-function" ]
-    if (is_linux && !use_udev) {
-      cflags += [ "-Wno-pointer-sign" ]
-    }
-  }
 }
 
 static_library("libusb") {
@@ -57,6 +46,15 @@
   deps = []
   include_dirs = [ "src/libusb/os" ]
 
+  config("libusb_warnings") {
+    if (is_clang) {
+      # guid_eq in windows_usb.c is unused.
+      cflags = [ "-Wno-unused-function" ]
+      if (is_linux && !use_udev) {
+        cflags += [ "-Wno-pointer-sign" ]
+      }
+    }
+  }
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   configs += [ ":libusb_warnings" ]