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

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 40f5713cf27d73b72005ab8d8313ed31539737da..96c0aae10519b19b84c2fb493ea9bb7a95da4d14 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -511,12 +511,15 @@ component("base") {
     "memory/shared_memory_android.cc",
     "memory/shared_memory_handle.h",
     "memory/shared_memory_handle_mac.cc",
+    "memory/shared_memory_handle_posix.cc",
     "memory/shared_memory_handle_win.cc",
     "memory/shared_memory_helper.cc",
     "memory/shared_memory_helper.h",
     "memory/shared_memory_mac.cc",
     "memory/shared_memory_nacl.cc",
     "memory/shared_memory_posix.cc",
+    "memory/shared_memory_tracker.cc",
+    "memory/shared_memory_tracker.h",
     "memory/shared_memory_win.cc",
     "memory/singleton.cc",
     "memory/singleton.h",
@@ -1381,6 +1384,7 @@ component("base") {
   # Mac or iOS.
   if (is_mac || is_ios) {
     sources -= [
+      "memory/shared_memory_handle_posix.cc",
       "memory/shared_memory_posix.cc",
       "native_library_posix.cc",
       "strings/sys_string_conversions_posix.cc",
@@ -1498,6 +1502,7 @@ component("base") {
       "mac/scoped_objc_class_swizzler.h",
       "mac/scoped_objc_class_swizzler.mm",
       "mac/scoped_typeref.h",
+      "memory/shared_memory_handle_posix.cc",
       "memory/shared_memory_posix.cc",
       "message_loop/message_pump_mac.h",
       "message_loop/message_pump_mac.mm",