Revert "reland 2: "mac: Run A/B experiment on SharedMemory mechanism for resource buffers.""

base/memory/shared_memory_mac.cc

Index: base/memory/shared_memory_mac.cc
diff --git a/base/memory/shared_memory_mac.cc b/base/memory/shared_memory_mac.cc
index 8f198dcbf75aaeab13c7ffcad774b0ec7e3ffbb7..799b8e3dfcda0acb8006e119d980bc411a17d6af 100644
--- a/base/memory/shared_memory_mac.cc
+++ b/base/memory/shared_memory_mac.cc
@@ -13,10 +13,7 @@
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
-#include "base/mac/mac_util.h"
 #include "base/mac/scoped_mach_vm.h"
-#include "base/metrics/field_trial.h"
-#include "base/metrics/histogram_macros.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/posix/safe_strerror.h"
 #include "base/process/process_metrics.h"
@@ -32,38 +29,6 @@ namespace base {
 
 namespace {
 
-const char kTrialName[] = "MacMemoryMechanism";
-const char kTrialMach[] = "Mach";
-const char kTrialPosix[] = "Posix";
-
-SharedMemoryHandle::Type GetABTestMechanism() {
-  static bool found_group = false;
-  static SharedMemoryHandle::Type group = SharedMemoryHandle::MACH;
-
-  if (found_group)
-    return group;
-
-  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::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);
-}
-
 // Returns whether the operation succeeded.
 // |new_handle| is an output variable, populated on success. The caller takes
 // ownership of the underlying memory object.
@@ -262,22 +227,6 @@ bool SharedMemory::CreateAnonymousPosix(size_t 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,
@@ -299,8 +248,6 @@ bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
   if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
     return false;
 
-  EmitMechanism(options.type);
-
   if (options.type == SharedMemoryHandle::MACH) {
     shm_ = SharedMemoryHandle(options.size);
     requested_size_ = options.size;