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

base/memory/shared_memory_posix.cc

Index: base/memory/shared_memory_posix.cc
diff --git a/base/memory/shared_memory_posix.cc b/base/memory/shared_memory_posix.cc
index 783bdfce86cd13eec8c133ca36fdeeb419dfabab..b3de60f8c350021933b5f13b5105d71bc56e1f74 100644
--- a/base/memory/shared_memory_posix.cc
+++ b/base/memory/shared_memory_posix.cc
@@ -14,6 +14,7 @@
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/logging.h"
+#include "base/memory/shared_memory_dump_provider.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/posix/safe_strerror.h"
 #include "base/process/process_metrics.h"
@@ -358,6 +359,7 @@ bool SharedMemory::MapAt(off_t offset, size_t bytes) {
     mapped_size_ = bytes;
     DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
         (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
+    SharedMemoryDumpProvider::GetInstance()->IncrementMemoryUsage(mapped_size_);

[haraken, 2016/11/30 04:39:26]

We want to get not only the mmaped size but also the effective size. Is there
any way to get an approximate number for the effective size?

   } else {
     memory_ = NULL;
   }
@@ -370,6 +372,7 @@ bool SharedMemory::Unmap() {
     return false;
 
   munmap(memory_, mapped_size_);
+  SharedMemoryDumpProvider::GetInstance()->DecrementMemoryUsage(mapped_size_);
   memory_ = NULL;
   mapped_size_ = 0;
   return true;