win: Add implementation of system_snapshot for Windows

compat/win/processor_power_information.h

 // 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,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef CRASHPAD_COMPAT_WIN_SYS_TIME_H_
-#define CRASHPAD_COMPAT_WIN_SYS_TIME_H_
+#ifndef CRASHPAD_COMPAT_WIN_PROCESSOR_POWER_INFORMATION_H_
+#define CRASHPAD_COMPAT_WIN_PROCESSOR_POWER_INFORMATION_H_
 
-struct timeval {
-  long tv_sec;
-  long tv_usec;
+// https://msdn.microsoft.com/en-us/library/windows/desktop/aa373184.aspx:
+// "Note that this structure definition was accidentally omitted from WinNT.h."
+struct PROCESSOR_POWER_INFORMATION {

[Mark Mentovai, 2015/02/27 22:27:42]

I thought that we could just put this into winnt.h and #include ../winnt.h,
since the doc says that the struct will show up in winnt.h in the future.

[scottmg, 2015/02/28 00:37:32]

Yeah, OK. I'm pretty skeptical that it'll ever get added, but I guess it's still
consistent with the docs.

+  ULONG Number;
+  ULONG MaxMhz;
+  ULONG CurrentMhz;
+  ULONG MhzLimit;
+  ULONG MaxIdleState;
+  ULONG CurrentIdleState;
 };
 
-#endif  // CRASHPAD_COMPAT_WIN_SYS_TIME_H_
+#endif  // CRASHPAD_COMPAT_WIN_PROCESSOR_POWER_INFORMATION_H_