Fixing remaining VC++ 2015 64-bit build breaks

chrome/app/chrome_watcher_client_unittest_win.cc

 // Copyright 2015 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_client_win.h"
 
 #include <windows.h>
 #include <string>
 
 #include "base/base_switches.h"
@@ skipping 152 matching lines @@
   }
 
  private:
   // Returns a command line to launch back into ChromeWatcherClientTestProcess.
   base::CommandLine GenerateCommandLine(HANDLE parent_handle,
                                         DWORD main_thread_id,
                                         HANDLE on_initialized_event) {
     base::CommandLine ret = base::GetMultiProcessTestChildBaseCommandLine();
     ret.AppendSwitchASCII(switches::kTestChildProcess,
                           "ChromeWatcherClientTestProcess");
-    ret.AppendSwitchASCII(kEventHandle,
-                          base::UintToString(reinterpret_cast<unsigned int>(
-                              on_initialized_event)));
+    // Cast through uintptr_t and then unsigned int to make the truncation
+    // explicit. Handles are size-of-pointer but are always 32-bit values.
     ret.AppendSwitchASCII(
-        kParentHandle,
-        base::UintToString(reinterpret_cast<unsigned int>(parent_handle)));
+        kEventHandle, base::UintToString(static_cast<unsigned int>(
+                          reinterpret_cast<uintptr_t>(on_initialized_event))));
+    ret.AppendSwitchASCII(kParentHandle,
+                          base::UintToString(static_cast<unsigned int>(
+                              reinterpret_cast<uintptr_t>(parent_handle))));
 
     // Our child does not actually need the main thread ID, but we verify here
     // that the correct ID is being passed from the client.
     EXPECT_EQ(::GetCurrentThreadId(), main_thread_id);
 
     ret.AppendSwitchASCII(kNamedEventSuffix,
                           base::UTF16ToASCII(NamedEventSuffix()));
     return ret;
   }
 
@@ skipping 78 matching lines @@
   // Give a broken implementation a chance to exit unexpectedly.
   ASSERT_FALSE(thread().WaitForResultWithTimeout(
       base::TimeDelta::FromMilliseconds(100), &result));
   ASSERT_TRUE(SignalExit());
   ASSERT_FALSE(thread().WaitForResult());
   int exit_code = 0;
   ASSERT_TRUE(
       thread().client().WaitForExitWithTimeout(base::TimeDelta(), &exit_code));
   ASSERT_EQ(0, exit_code);
 }