Move non-content specific parts of content::MachBroker into base::MachPortBroker.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 6355bf7298a5b70fd7d0f3555f0364515c62a28a..61a36c8d180f06415a4410ede668f720a738dec0 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -413,6 +413,8 @@ component("base") {
     "mac/mac_util.mm",
     "mac/mach_logging.cc",
     "mac/mach_logging.h",
+    "mac/mach_port_broker.h",
+    "mac/mach_port_broker.mm",
     "mac/objc_property_releaser.h",
     "mac/objc_property_releaser.mm",
     "mac/os_crash_dumps.cc",
@@ -1182,6 +1184,7 @@ component("base") {
       "trace_event/malloc_dump_provider.cc",
       "trace_event/malloc_dump_provider.h",
     ]
+    libs = [ "bsm" ]
   }
 
   # Mac or iOS.
@@ -1626,6 +1629,7 @@ test("base_unittests") {
     "mac/foundation_util_unittest.mm",
     "mac/libdispatch_task_runner_unittest.cc",
     "mac/mac_util_unittest.mm",
+    "mac/mach_port_broker_unittest.cc",
     "mac/objc_property_releaser_unittest.mm",
     "mac/scoped_nsobject_unittest.mm",
     "mac/scoped_objc_class_swizzler_unittest.mm",