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

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 7081e03d8b924d326cc15afbdec95e2333a2e8f4..e1f8af3b70289728eae8f471126fa6558b387e88 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -30021,15 +30021,6 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram name="OSX.SharedMemory.Mechanism" enum="OSXSharedMemoryMechanism">
-  <owner>erikchen@chromium.org</owner>
-  <summary>
-    A histogram entry is emitted each time a base::SharedMemory object is
-    constructed. The value of the entry indicates the mechanism used to back the
-    shared memory region.
-  </summary>
-</histogram>
-
 <histogram name="OSX.SystemHotkeyMap.LoadSuccess" enum="BooleanSuccess">
   <owner>erikchen@chromium.org</owner>
   <summary>
@@ -67956,15 +67947,6 @@ To add a new entry, add it with any value and run test to compute valid value.
   </int>
 </enum>
 
-<enum name="OSXSharedMemoryMechanism" type="int">
-  <int value="0" label="POSIX">
-    The shared memory region is backed by a POSIX fd.
-  </int>
-  <int value="1" label="MACH">
-    The shared memory region is backed by a Mach memory object.
-  </int>
-</enum>
-
 <enum name="OtherPossibleUsernamesUsage" type="int">
   <int value="0" label="Nothing to Autofill"/>
   <int value="1" label="No other possible usernames"/>