Revert "mac: Run A/B experiment on SharedMemory mechanism for resource buffers."

base/memory/shared_memory_handle.h

Index: base/memory/shared_memory_handle.h
diff --git a/base/memory/shared_memory_handle.h b/base/memory/shared_memory_handle.h
index 49398a4a9a96cf066e8ff830b703c89c16cb9626..b3dfc8fa380e220a62e8384dfb09000e975a1386 100644
--- a/base/memory/shared_memory_handle.h
+++ b/base/memory/shared_memory_handle.h
@@ -75,15 +75,12 @@ class BASE_EXPORT SharedMemoryHandle {
 #else
 class BASE_EXPORT SharedMemoryHandle {
  public:
-  // The values of these enums must not change, as they are used by the
-  // histogram OSX.SharedMemory.Mechanism.
   enum Type {
     // The SharedMemoryHandle is backed by a POSIX fd.
     POSIX,
     // The SharedMemoryHandle is backed by the Mach primitive "memory object".
     MACH,
   };
-  static const int TypeMax = 2;
 
   // The format that should be used to transmit |Type| over the wire.
   typedef int TypeWireFormat;