win: Fix a few sign mismatch warnings in crashpad.

snapshot/win/process_reader_win.cc

 // Copyright 2015 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 118 matching lines @@
                            reinterpret_cast<process_types::TEB<Traits>*>(
                                NtCurrentTeb())->ClientId.UniqueThread;
 
   if (is_current_thread) {
     DCHECK(suspension_state == ProcessSuspensionState::kRunning);
     thread->suspend_count = 0;
     DCHECK(!is_64_reading_32);
     CaptureContext(&thread->context.native);
   } else {
     DWORD previous_suspend_count = SuspendThread(thread_handle);
-    if (previous_suspend_count == -1) {
+    if (previous_suspend_count == static_cast<DWORD>(-1)) {

[Mark Mentovai, 2015/12/08 22:05:59]

-1u?

[Nico, 2015/12/08 22:07:12]

MSDN says that SuspendThread returns "(DWORD)-1" on error, I figured it's nicer
to look closer to that.

       PLOG(ERROR) << "SuspendThread";
       return false;
     }
     DCHECK(previous_suspend_count > 0 ||
            suspension_state == ProcessSuspensionState::kRunning);
     thread->suspend_count =
         previous_suspend_count -
         (suspension_state == ProcessSuspensionState::kSuspended ? 1 : 0);
 
     memset(&thread->context, 0, sizeof(thread->context));
@@ skipping 254 matching lines @@
         thread.stack_region_size = 0;
       } else {
         thread.stack_region_size = base - limit;
       }
     }
     threads_.push_back(thread);
   }
 }
 
 }  // namespace crashpad