Pass StatsTable shared memory via global descriptors on Posix rather than using named shared memory.

ipc/ipc_descriptors.h

Index: ipc/ipc_descriptors.h
diff --git a/ipc/ipc_descriptors.h b/ipc/ipc_descriptors.h
index b766bbbe76958f97b62e832c185a47ec307aaa60..9dcff8ceb1394879fe4077321a1dee97af00e6b7 100644
--- a/ipc/ipc_descriptors.h
+++ b/ipc/ipc_descriptors.h
@@ -9,6 +9,10 @@
 // base::GlobalDescriptors object (see base/posix/global_descriptors.h)
 enum {
   kPrimaryIPCChannel = 0,
+  kStatsTableSharedMemFd,
+
+  // The first key that can be use to register descriptors.
+  kIPCDescriptorMax
 };
 
 #endif  // IPC_IPC_DESCRIPTORS_H_