Fix a bunch of clang warnings/errors.

base/mach_ipc_mac.h

Index: base/mach_ipc_mac.h
diff --git a/base/mach_ipc_mac.h b/base/mach_ipc_mac.h
index 91b9729db68451fd23cfc1c6e9d6f581ae99dcbf..d506a00c89d657e0c2262d9a8de43bc85dfcc9ca 100644
--- a/base/mach_ipc_mac.h
+++ b/base/mach_ipc_mac.h
@@ -114,12 +114,6 @@ class MachMsgPortDescriptor : public mach_msg_port_descriptor_t {
     return disposition;
   }
 
-  // We're just a simple wrapper for mach_msg_port_descriptor_t
-  // and have the same memory layout
-  operator mach_msg_port_descriptor_t&() {
-    return *this;
-  }
-
   // For convenience
   operator mach_port_t() const {
     return GetMachPort();