Add comment that describes handle ownership confusion for base::Process.

On Windows, base::Process takes ownership of the input |handle|. On Posix, it
does not.

Bug: 
Change-Id: I3d53faba3ec46f23afc89811a7ebec603c2dce7b
Reviewed-on: https://chromium-review.googlesource.com/661378
Reviewed-by: Daniel Cheng <[email protected]>
Commit-Queue: Erik Chen <[email protected]>
Cr-Commit-Position: refs/heads/master@{#501075}
diff --git a/base/process/process.h b/base/process/process.h
index a4d77dfa..c46ec7c0 100644
--- a/base/process/process.h
+++ b/base/process/process.h
@@ -45,6 +45,8 @@
 // end up pointing to the wrong process.
 class BASE_EXPORT Process {
  public:
+  // On Windows, this takes ownership of |handle|. On POSIX, this does not take
+  // ownership of |handle|.
   explicit Process(ProcessHandle handle = kNullProcessHandle);
 
   Process(Process&& other);