Share field trial allocator on MacOS

base/metrics/field_trial.cc

Index: base/metrics/field_trial.cc
diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc
index f11ef3535364ea609421842b99504373d36e0b52..2f28d725dfbc494a5fc3a93475d9cd299cdfb793 100644
--- a/base/metrics/field_trial.cc
+++ b/base/metrics/field_trial.cc
@@ -28,7 +28,7 @@
 #define POSIX_WITH_ZYGOTE 1
 #endif
 
-#if defined(POSIX_WITH_ZYGOTE)
+#if defined(POSIX_WITH_ZYGOTE) || defined(OS_MACOSX)
 #include "base/posix/global_descriptors.h"
 #endif
 
@@ -269,7 +269,7 @@ HANDLE CreateReadOnlyHandle(FieldTrialList::FieldTrialAllocator* allocator) {
 }
 #endif
 
-#if defined(POSIX_WITH_ZYGOTE)
+#if defined(POSIX_WITH_ZYGOTE) || defined(OS_MACOSX)
 int CreateReadOnlyHandle(FieldTrialList::FieldTrialAllocator* allocator) {
   SharedMemoryHandle new_handle;
   allocator->shared_memory()->ShareReadOnlyToProcess(GetCurrentProcessHandle(),
@@ -790,7 +790,7 @@ void FieldTrialList::CreateTrialsFromCommandLine(
   }
 #endif
 
-#if defined(POSIX_WITH_ZYGOTE)
+#if defined(POSIX_WITH_ZYGOTE) || defined(OS_MACOSX)
   // If we failed to create trials from the descriptor, fallback to the command
   // line. Otherwise we're good -- return.
   if (CreateTrialsFromDescriptor(fd_key))
@@ -805,7 +805,7 @@ void FieldTrialList::CreateTrialsFromCommandLine(
   }
 }
 
-#if defined(POSIX_WITH_ZYGOTE)
+#if defined(POSIX_WITH_ZYGOTE) || defined(OS_MACOSX)
 // static
 bool FieldTrialList::CreateTrialsFromDescriptor(int fd_key) {
   if (!kUseSharedMemoryForFieldTrials)
@@ -861,7 +861,7 @@ void FieldTrialList::CopyFieldTrialStateToFlags(
   if (!global_)
     return;
 
-#if defined(OS_WIN) || defined(POSIX_WITH_ZYGOTE)
+#if defined(OS_WIN) || defined(POSIX_WITH_ZYGOTE) || defined(OS_MACOSX)
   // Use shared memory to pass the state if the feature is enabled, otherwise
   // fallback to passing it via the command line as a string.
   if (kUseSharedMemoryForFieldTrials) {
@@ -1154,6 +1154,9 @@ void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() {
   SharedMemoryCreateOptions options;
   options.size = kFieldTrialAllocationSize;
   options.share_read_only = true;
+#if defined(OS_MACOSX)
+  options.type = SharedMemoryHandle::POSIX;
+#endif
 
   std::unique_ptr<SharedMemory> shm(new SharedMemory());
   if (!shm->Create(options))
@@ -1171,7 +1174,7 @@ void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() {
     AddToAllocatorWhileLocked(registered.second);
   }
 
-#if defined(OS_WIN) || defined(POSIX_WITH_ZYGOTE)
+#if defined(OS_WIN) || defined(POSIX_WITH_ZYGOTE) || defined(OS_MACOSX)
   // Set |readonly_allocator_handle_| so we can pass it to be inherited and
   // via the command line.
   global_->readonly_allocator_handle_ =