[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

base/memory/shared_memory_handle_mac.cc

Index: base/memory/shared_memory_handle_mac.cc
diff --git a/base/memory/shared_memory_handle_mac.cc b/base/memory/shared_memory_handle_mac.cc
index 9dfd3c1aeacbbc1d89fb6b09ffad5c5eec3df23a..7bd75a92905b34a7e85209322bdf97d782dc84a2 100644
--- a/base/memory/shared_memory_handle_mac.cc
+++ b/base/memory/shared_memory_handle_mac.cc
@@ -216,4 +216,15 @@ void SharedMemoryHandle::CopyRelevantData(const SharedMemoryHandle& handle) {
   }
 }
 
+bool GetIDFromSharedMemoryHandle(const SharedMemoryHandle& handle,
+                                 SharedMemoryHandleID* id) {
+  // TODO(hajimehoshi): Implement this.
+  return true;
+}
+
+std::string GetSharedMemoryHandleIDString(const SharedMemoryHandleID& id) {
+  // TODO(hajimehoshi): Implement this.
+  return "";
+}
+
 }  // namespace base