Performance patch to always use Mach shared memory on OS X instead of POSIX wrapper

chromium-mach-shared-memory.patch

diff --git a/base/memory/shared_memory_mac.cc b/base/memory/shared_memory_mac.cc
index 8f198dc..9f966c8 100644
--- a/base/memory/shared_memory_mac.cc
+++ b/base/memory/shared_memory_mac.cc
@@ -32,6 +32,7 @@ namespace base {

 namespace {

+#if 0
 const char kTrialName[] = "MacMemoryMechanism";
 const char kTrialMach[] = "Mach";
 const char kTrialPosix[] = "Posix";
@@ -57,7 +58,8 @@ SharedMemoryHandle::Type GetABTestMechanism() {

   return group;
 }
-
+#endif
+
 // Emits a histogram entry indicating which type of SharedMemory was created.
 void EmitMechanism(SharedMemoryHandle::Type type) {
   UMA_HISTOGRAM_ENUMERATION("OSX.SharedMemory.Mechanism", type,
@@ -248,7 +250,7 @@ int SharedMemory::GetFdFromSharedMemoryHandle(
 }

 bool SharedMemory::CreateAndMapAnonymous(size_t size) {
-  return CreateAnonymous(size) && Map(size);
+  return CreateAndMapAnonymousMach(size);
 }

 bool SharedMemory::CreateAndMapAnonymousPosix(size_t size) {
@@ -269,7 +271,7 @@ bool SharedMemory::CreateAndMapAnonymousMach(size_t size) {
     // 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();
+    options.type = SharedMemoryHandle::MACH;//GetABTestMechanism();
   } else {
     // Mach shared memory isn't supported on OSX 10.6 or older.
     options.type = SharedMemoryHandle::POSIX;