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

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 8237b44411ca34cd5913d58d699398fad4f0f8cf..8eae811a1085e3d2b11330c7761a3aed2cd4af21 100644
--- a/base/memory/shared_memory_mac.cc
+++ b/base/memory/shared_memory_mac.cc
@@ -17,6 +17,7 @@
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_mach_vm.h"
 #include "base/memory/shared_memory_helper.h"
+#include "base/memory/shared_memory_tracker.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/posix/eintr_wrapper.h"
@@ -205,6 +206,7 @@ bool SharedMemory::MapAt(off_t offset, size_t bytes) {
     DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
                       (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
     mapped_memory_mechanism_ = shm_.type_;
+    SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
   } else {
     last_error_ = SharedMemoryError::MMAP_FAILED;
     memory_ = NULL;
@@ -227,7 +229,7 @@ bool SharedMemory::Unmap() {
                          mapped_size_);
       break;
   }
-
+  SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
   memory_ = NULL;
   mapped_size_ = 0;
   return true;