Fixing remaining VC++ 2015 64-bit build breaks

chrome/app/chrome_watcher_command_line_win.cc

 // Copyright (c) 2014 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 "chrome/app/chrome_watcher_command_line_win.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/common/chrome_switches.h"
 #include "content/public/common/content_switches.h"
 
 namespace {
 
 const char kOnIninitializedEventHandleSwitch[] = "on-initialized-event-handle";
 const char kParentHandleSwitch[] = "parent-handle";
 const char kMainThreadIdSwitch[] = "main-thread-id";
 
 void AppendHandleSwitch(const std::string& switch_name,
                         HANDLE handle,
                         base::CommandLine* command_line) {
-  command_line->AppendSwitchASCII(
-      switch_name, base::UintToString(reinterpret_cast<uint32_t>(handle)));
+  // Cast through uintptr_t and then uint32_t to make the truncation
+  // explicit. Handles are size-of-pointer but are always 32-bit values.
+  command_line->AppendSwitchASCII(switch_name,
+                                  base::UintToString(static_cast<uint32_t>(
+                                      reinterpret_cast<uintptr_t>(handle))));
 }
 
 uint32_t ReadUintSwitch(const base::CommandLine& command_line,
                             const std::string& switch_name) {
   std::string switch_string = command_line.GetSwitchValueASCII(switch_name);
   unsigned int switch_uint = 0;
   if (switch_string.empty() ||
       !base::StringToUint(switch_string, &switch_uint)) {
     DLOG(ERROR) << "Missing or invalid " << switch_name << " argument.";
     return 0;
@@ skipping 71 matching lines @@
       !parent_process->IsValid()) {
     // If one was valid and not the other, free the valid one.
     on_initialized_event->Close();
     parent_process->Close();
     *main_thread_id = 0;
     return false;
   }
 
   return true;
 }