Make ProcessWatcher use kqueues on Mac.

base/file_util.h

Index: base/file_util.h
diff --git a/base/file_util.h b/base/file_util.h
index 9eb172916b5fca69d8be94507465d000e7d9fede..543a86c7779d608c39aabe8cc6d9ddbcff7d283d 100644
--- a/base/file_util.h
+++ b/base/file_util.h
@@ -371,6 +371,20 @@ class ScopedFILEClose {
 
 typedef scoped_ptr_malloc<FILE, ScopedFILEClose> ScopedFILE;
 
+#if defined(OS_POSIX)
+// A class to handle auto-closing of FDs.
+class ScopedFDClose {
+ public:
+  inline void operator()(int* x) const {
+    if (x) {
+      close(*x);
+    }
+  }
+};
+
+typedef scoped_ptr_malloc<int, ScopedFDClose> ScopedFD;
+#endif  // OS_POSIX
+
 // A class for enumerating the files in a provided path. The order of the
 // results is not guaranteed.
 //