mac: Add a mode to crashpad_handler to run from launchd

handler/mac/exception_handler_server.h

Index: handler/mac/exception_handler_server.h
diff --git a/handler/mac/exception_handler_server.h b/handler/mac/exception_handler_server.h
index 05c4056fe19a41e2fb933422b503edeafac5735f..df9d5a0d0dcc3d5af620ef2f10692b239f203887 100644
--- a/handler/mac/exception_handler_server.h
+++ b/handler/mac/exception_handler_server.h
@@ -32,20 +32,26 @@ class ExceptionHandlerServer {
   //!
   //! \param[in] receive_port The port that exception messages and no-senders
   //!     notifications will be received on.
-  explicit ExceptionHandlerServer(
-      base::mac::ScopedMachReceiveRight receive_port);
+  //! \param[in] launchd If `true`, the exception handler is being run from
+  //!     launchd. \a receive_port is not monitored for no-senders
+  //!     notifications, and instead, the expected “quit” signal is receipt of
+  //!     `SIGTERM`.
+  ExceptionHandlerServer(base::mac::ScopedMachReceiveRight receive_port,
+                         bool launchd);
   ~ExceptionHandlerServer();
 
   //! \brief Runs the exception-handling server.
   //!
   //! \param[in] exception_interface An object to send exception messages to.
   //!
-  //! This method monitors the receive port for exception messages and
-  //! no-senders notifications. It continues running until it has no more
-  //! clients, indicated by the receipt of a no-senders notification. It is
-  //! important to assure that a send right exists in a client (or has been
-  //! queued by `mach_msg()` to be sent to a client) prior to calling this
-  //! method, or it will detect that it is sender-less and return immediately.
+  //! This method monitors the receive port for exception messages and, if
+  //! not being run by launchd, no-senders notifications. It continues running
+  //! until it has no more clients, indicated by the receipt of a no-senders
+  //! notification, or if being run by launchd, receipt of `SIGTERM`. When not
+  //! being run by launchd, it is important to assure that a send right exists
+  //! in a client (or has been queued by `mach_msg()` to be sent to a client)
+  //! prior to calling this method, or it will detect that it is sender-less and
+  //! return immediately.
   //!
   //! All exception messages will be passed to \a exception_interface.
   //!
@@ -59,6 +65,7 @@ class ExceptionHandlerServer {
 
  private:
   base::mac::ScopedMachReceiveRight receive_port_;
+  bool launchd_;
 
   DISALLOW_COPY_AND_ASSIGN(ExceptionHandlerServer);
 };