Add generic.total_physical_bytes property to MallocExtension

third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h

Index: third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h
diff --git a/third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h b/third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h
index d1148ded34424a2e22ba9c7dc0018bfeb3b3ec7b..0a9b4ed84021bbcaba86a263da13be001e08d90d 100644
--- a/third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h
+++ b/third_party/tcmalloc/chromium/src/gperftools/malloc_extension.h
@@ -159,6 +159,14 @@ class PERFTOOLS_DLL_DECL MallocExtension {
   //            freed memory regions
   //      This property is not writable.
   //
+  //  "generic.total_physical_bytes"
+  //      Estimate of total bytes of the physical memory usage by the
+  //      allocator ==
+  //            current_allocated_bytes +
+  //            fragmentation +
+  //            metadata
+  //      This property is not writable.
+  //
   // tcmalloc
   // --------
   // "tcmalloc.max_total_thread_cache_bytes"