Fix some extern usage in .cc files.

content/common/sandbox_init_mac.h

Index: content/common/sandbox_init_mac.h
diff --git a/content/common/sandbox_init_mac.h b/content/common/sandbox_init_mac.h
index 4bbabb397b62991574a6a2c5b0f3c68e4d993a58..8f860efd048daa9196d88e82c5e573ee6ab62b24 100644
--- a/content/common/sandbox_init_mac.h
+++ b/content/common/sandbox_init_mac.h
@@ -15,14 +15,6 @@ namespace content {
 // returned.
 bool InitializeSandbox();
 
-// The bootstrap server name of the real bootstrap port. This is never used
-// with bootstrap_register, but is instead used with a POLICY_SUBSTITUTE_PORT
-// in the bootstrap sandbox. In child processes, the the launchd/bootstrap
-// sandbox will have replaced the bootstrap port with one controlled by the
-// interception server. This server name can be used to request the original
-// server, from the browser, in NPAPI plugins.
-extern const char kBootstrapPortNameForNPAPIPlugins[];
-
 }  // namespace content
 
 #endif  // CONTENT_COMMON_SANDBOX_INIT_MAC_H_