Convert device::UsbConfigDescriptor and friends to structs.

device/usb/BUILD.gn

Index: device/usb/BUILD.gn
diff --git a/device/usb/BUILD.gn b/device/usb/BUILD.gn
index 0e97bfec0d5d1196118841009353707c51461d3b..385bcb961d5d2c6564c236638a9a405bdc93e609 100644
--- a/device/usb/BUILD.gn
+++ b/device/usb/BUILD.gn
@@ -9,6 +9,8 @@ source_set("usb") {
   sources = [
     "usb_context.cc",
     "usb_context.h",
+    "usb_descriptors.cc",
+    "usb_descriptors.h",
     "usb_device_impl.cc",
     "usb_device_impl.h",
     "usb_device.h",
@@ -21,9 +23,6 @@ source_set("usb") {
     "usb_error.h",
     "usb_ids.cc",
     "usb_ids.h",
-    "usb_interface.h",
-    "usb_interface_impl.cc",
-    "usb_interface_impl.h",
     "usb_service.h",
     "usb_service_impl.cc",
     generated_ids,