[sms] Add a new SharingMessage proto for fetching SMS messages remotely

Per instructions on the Unido design doc [1], this is the first step in
the process of creating a new Unido feature:

1) Add a new SharingMessage to the proto and update metrics mapping
2) Add your new SharingFCMHandler in SharingService constructor
3) Add a new feature in DeviceInfoSpecifics.EnabledFeatures
4) Add your enabled feature to SharingDeviceRegistration
5) Use SharingService to list device candidates, and use the new SendMessageToDevice to send messages

Steps (2-5) will follow in separate CLs, to ease reviewing and ease
other features tracking how to integrate.

[1] https://docs.google.com/document/d/1tvrKCEOaQuZv_j6j61ij_r9sjFlI25x8M8rIRL1DTsA/edit#

Design Doc: https://docs.google.com/document/d/1da8CjO71DlFbBzDcSosFRXTvDsKII_XMCohpZLQ_QbM/edit?userstoinvite=himanshujaju%40google.com&ts=5da89bb1&actionButton=1

Bug: 1015645
Change-Id: If41831a2e71ec88b4771c739be18fd17c18ac6f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1867444
Auto-Submit: Sam Goto <goto@chromium.org>
Commit-Queue: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Alex Chau <alexchau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707917}

chrome/browser/sharing/proto/BUILD.gn

@@ -16,5 +16,6 @@ proto_library("proto") {
     "click_to_call_message.proto",
     "shared_clipboard_message.proto",
     "sharing_message.proto",
+    "sms_fetch_request.proto",
   ]
 }

chrome/browser/sharing/proto/sharing_message.proto

@@ -6,6 +6,7 @@ syntax = "proto3";
 
 import "click_to_call_message.proto";
 import "shared_clipboard_message.proto";
+import "sms_fetch_request.proto";
 
 package chrome_browser_sharing;
 
@@ -22,9 +23,11 @@ enum MessageType {
   ACK_MESSAGE = 2;
   CLICK_TO_CALL_MESSAGE = 3;
   SHARED_CLIPBOARD_MESSAGE = 4;
+  SMS_FETCH_REQUEST = 5;
 }
 
 // Message for sending between devices in Sharing.
+// Next tag: 9
 message SharingMessage {
   // Identifier of sender. required except for AckMessage.
   string sender_guid = 1;
@@ -35,6 +38,7 @@ message SharingMessage {
     AckMessage ack_message = 3;
     ClickToCallMessage click_to_call_message = 4;
     SharedClipboardMessage shared_clipboard_message = 5;
+    SmsFetchRequest sms_fetch_request = 8;
   }
 
   // RecipientInfo for responding an AckMessage to the sender. optional.

chrome/browser/sharing/proto/sms_fetch_request.proto

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto3";
+
+package chrome_browser_sharing;
+
+// Required in Chrome.
+option optimize_for = LITE_RUNTIME;
+
+// Request message to fetch a SMS from a remote device.
+message SmsFetchRequest {}

chrome/browser/sharing/sharing_metrics.cc

@@ -59,6 +59,8 @@ chrome_browser_sharing::MessageType SharingPayloadCaseToMessageType(
       return chrome_browser_sharing::CLICK_TO_CALL_MESSAGE;
     case chrome_browser_sharing::SharingMessage::kSharedClipboardMessage:
       return chrome_browser_sharing::SHARED_CLIPBOARD_MESSAGE;
+    case chrome_browser_sharing::SharingMessage::kSmsFetchRequest:
+      return chrome_browser_sharing::SMS_FETCH_REQUEST;
   }
   // For proto3 enums unrecognized enum values are kept when parsing, and a new
   // payload case received over the network would not default to

tools/metrics/histograms/enums.xml

@@ -56254,6 +56254,7 @@ Called by update_net_trust_anchors.py.-->
   <int value="2" label="Ack"/>
   <int value="3" label="ClickToCall"/>
   <int value="4" label="SharedClipboard"/>
+  <int value="5" label="SmsFetchRequest"/>
 </enum>
 
 <enum name="SharingSendMessageResult">

tools/metrics/histograms/histograms.xml

@@ -179262,6 +179262,7 @@ regressions. -->
   <suffix name="CLICK_TO_CALL_MESSAGE" label="Click To Call Message"/>
   <suffix name="PING_MESSAGE" label="Ping Message"/>
   <suffix name="SHARED_CLIPBOARD_MESSAGE" label="Shared Clipboard Message"/>
+  <suffix name="SMS_FETCH_REQUEST" label="SMS Fetch Request"/>
   <suffix name="UNKNOWN_MESSAGE" label="Unknown Message"/>
   <affected-histogram name="Sharing.MessageAckTime"/>
   <affected-histogram name="Sharing.MessageReceivedType"/>