Misc truncation fixes for gn builds with VS 2015

content/browser/renderer_host/p2p/socket_host_test_utils.cc

 // Copyright (c) 2013 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.
 
 #include "content/browser/renderer_host/p2p/socket_host_test_utils.h"
 
 #include "base/logging.h"
 #include "base/sys_byteorder.h"
 #include "base/thread_task_runner_handle.h"
 #include "net/base/completion_callback.h"
@@ skipping 178 matching lines @@
     (*packet)[i] = rand() % 256;
   }
   // Always set the first bit to ensure that generated packet is not
   // valid STUN packet.
   (*packet)[0] = (*packet)[0] | 0x80;
 }
 
 static void CreateStunPacket(std::vector<char>* packet, uint16 type) {
   CreateRandomPacket(packet);
   *reinterpret_cast<uint16*>(&*packet->begin()) = base::HostToNet16(type);
-  *reinterpret_cast<uint16*>(&*packet->begin() + 2) =
-      base::HostToNet16(packet->size() - kStunHeaderSize);
+  *reinterpret_cast<uint16*>(&*packet->begin() + 2) = base::HostToNet16(
+      base::checked_cast<uint16>(packet->size() - kStunHeaderSize));
   *reinterpret_cast<uint32*>(&*packet->begin() + 4) =
       base::HostToNet32(kStunMagicCookie);
 }
 
 void CreateStunRequest(std::vector<char>* packet) {
   CreateStunPacket(packet, kStunBindingRequest);
 }
 
 void CreateStunResponse(std::vector<char>* packet) {
   CreateStunPacket(packet, kStunBindingResponse);
 }
 
 void CreateStunError(std::vector<char>* packet) {
   CreateStunPacket(packet, kStunBindingError);
 }
 
 net::IPEndPoint ParseAddress(const std::string& ip_str, uint16 port) {
   net::IPAddressNumber ip;
   EXPECT_TRUE(net::ParseIPLiteralToNumber(ip_str, &ip));
   return net::IPEndPoint(ip, port);
 }