Reland of base: Make shared memory backed by Mach primitives by default.

base/memory/shared_memory_mac.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/memory/shared_memory.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <mach/mach_vm.h>
 #include <sys/mman.h>
@@ skipping 35 matching lines @@
 
   const std::string group_name =
       base::FieldTrialList::FindFullName(kTrialName);
   if (group_name == kTrialMach) {
     group = SharedMemoryHandle::MACH;
     found_group = true;
   } else if (group_name == kTrialPosix) {
     group = SharedMemoryHandle::POSIX;
     found_group = true;
   } else {
-    group = SharedMemoryHandle::POSIX;
+    group = SharedMemoryHandle::MACH;
   }
 
   return group;
 }
 
 // Emits a histogram entry indicating which type of SharedMemory was created.
 void EmitMechanism(SharedMemoryHandle::Type type) {
   UMA_HISTOGRAM_ENUMERATION("OSX.SharedMemory.Mechanism", type,
                             SharedMemoryHandle::TypeMax);
 }
@@ skipping 101 matching lines @@
         return false;
       }
     }
   }
   return true;
 }
 
 }  // namespace
 
 SharedMemoryCreateOptions::SharedMemoryCreateOptions()
-    : type(SharedMemoryHandle::POSIX),
+    : type(SharedMemoryHandle::MACH),
       size(0),
       executable(false),
-      share_read_only(false) {}
+      share_read_only(false) {
+  if (mac::IsOSLionOrLater()) {
+    // A/B test the mechanism. Once the experiment is over, this will always be
+    // set to SharedMemoryHandle::MACH.
+    // http://crbug.com/547261
+    type = GetABTestMechanism();
+  } else {
+    // Mach shared memory isn't supported on OSX 10.6 or older.
+    type = SharedMemoryHandle::POSIX;
+  }
+}
 
 SharedMemory::SharedMemory()
     : mapped_memory_mechanism_(SharedMemoryHandle::POSIX),
       readonly_mapped_file_(-1),
       mapped_size_(0),
       memory_(NULL),
       read_only_(false),
       requested_size_(0) {}
 
 SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
@@ skipping 64 matching lines @@
   return CreateAnonymousPosix(size) && Map(size);
 }
 
 bool SharedMemory::CreateAnonymousPosix(size_t size) {
   SharedMemoryCreateOptions options;
   options.type = SharedMemoryHandle::POSIX;
   options.size = size;
   return Create(options);
 }
 
-bool SharedMemory::CreateAndMapAnonymousMach(size_t size) {
-  SharedMemoryCreateOptions options;
-
-  if (mac::IsOSLionOrLater()) {
-    // A/B test the mechanism. Once the experiment is over, this will always be
-    // set to SharedMemoryHandle::MACH.
-    // http://crbug.com/547261
-    options.type = GetABTestMechanism();
-  } else {
-    // Mach shared memory isn't supported on OSX 10.6 or older.
-    options.type = SharedMemoryHandle::POSIX;
-  }
-  options.size = size;
-  return Create(options) && Map(size);
-}
-
 // static
 bool SharedMemory::GetSizeFromSharedMemoryHandle(
     const SharedMemoryHandle& handle,
     size_t* size) {
   return handle.GetSize(size);
 }
 
 // Chromium mostly only uses the unique/private shmem as specified by
 // "name == L"". The exception is in the StatsTable.
 bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
@@ skipping 205 matching lines @@
 
   if (close_self) {
     Unmap();
     Close();
   }
 
   return true;
 }
 
 }  // namespace base