Include the raw data for incoming GCM messages.

The optional raw_data field in the DataMessageStanza MCS proto will be
empty for conventional messages, but will contain data for other types
of messages, e.g. Web Push protocol messages.

BUG=468040

Review URL: https://codereview.chromium.org/1235193003

Cr-Commit-Position: refs/heads/master@{#339860}
4 files changed