[OnionSoup] Remove [Native] content.mojom.PlatformNotificationData

Currently service_worker.mojom defines a [Native] mojom struct
content.mojom.PlatformNotificationData using the legacy IPC struct
traits for the native struct content::PlatformNotificationData.

However, there is already existing a mojom struct
blink.mojom.NotificationData which is typemapped with
content::PlatformNotificationData, it's exactly fit to our needs, so,
this CL starts to use blink.mojom.NotificationData then removes
the [Native] content.mojom.PlatformNotificationData and the
corresponding legacy IPC struct traits.

BUG=789854

Change-Id: I20549a8feb3575341661b92a5993bf758e6174e1
Reviewed-on: https://chromium-review.googlesource.com/1149714
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Han Leon <leon.han@intel.com>
Cr-Commit-Position: refs/heads/master@{#578321}
6 files changed