Fix a crash of GetPrinterCapsAndDefaults returns after the calling printer is deleted.

chrome/service/cloud_print/printer_job_handler.h

Index: chrome/service/cloud_print/printer_job_handler.h
diff --git a/chrome/service/cloud_print/printer_job_handler.h b/chrome/service/cloud_print/printer_job_handler.h
index a9de1787c96652d49f276f26c8b292e3486dc35a..ce48d61245fcd31301b3f564e164a28d37ed3a6c 100644
--- a/chrome/service/cloud_print/printer_job_handler.h
+++ b/chrome/service/cloud_print/printer_job_handler.h
@@ -12,6 +12,7 @@
 
 #include "base/file_path.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/message_loop_proxy.h"
 #include "base/threading/thread.h"
 #include "base/time.h"
@@ -289,6 +290,7 @@ class PrinterJobHandler : public base::RefCountedThreadSafe<PrinterJobHandler>,
   JobStatusUpdaterList job_status_updater_list_;
 
   base::TimeTicks last_job_fetch_time_;
+  base::WeakPtrFactory<PrinterJobHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrinterJobHandler);
 };