[Mac] Remove base::LaunchSynchronize and rewrite content::MachBroker.

content/content_browser.gypi

Index: content/content_browser.gypi
diff --git a/content/content_browser.gypi b/content/content_browser.gypi
index 017d291d530393728c2d8c1340df23c972fd2da9..1de3993d1bf1bb81bdab83de8cb18e835c883ee9 100644
--- a/content/content_browser.gypi
+++ b/content/content_browser.gypi
@@ -587,7 +587,7 @@
     'browser/loader/throttling_resource_handler.h',
     'browser/loader/transfer_navigation_resource_throttle.cc',
     'browser/loader/transfer_navigation_resource_throttle.h',
-    'browser/mach_broker_mac.cc',
+    'browser/mach_broker_mac.mm',
     'browser/mach_broker_mac.h',
     'browser/media_devices_monitor.cc',
     'browser/media/media_internals.cc',
@@ -1201,6 +1201,11 @@
       'dependencies': [
         '../third_party/sudden_motion_sensor/sudden_motion_sensor.gyp:sudden_motion_sensor',
       ],
+      'link_settings': {
+        'libraries': [
+          '$(SDKROOT)/usr/lib/libbsm.dylib',
+        ],
+      },
     }],
     ['chromeos==1', {
       'dependencies': [