base: Introduce SharedMemoryTracker for POSIX (but not macOS)

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index fc39018efc63064b454280af10a0892817190c72..4e1b0a5d24e347a21d6dffb85f137d847ab5c308 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -485,6 +485,8 @@ component("base") {
     "macros.h",
     "md5.cc",
     "md5.h",
+    "memory/address_hasher.cc",
+    "memory/address_hasher.h",
     "memory/aligned_memory.cc",
     "memory/aligned_memory.h",
     "memory/discardable_memory.cc",
@@ -1577,6 +1579,13 @@ component("base") {
     sources += [ "power_monitor/power_monitor_device_source_posix.cc" ]
   }
 
+  if (is_posix && !is_mac && !is_nacl) {
+    sources += [
+      "memory/shared_memory_tracker.cc",
+      "memory/shared_memory_tracker.h",
+    ]
+  }
+
   if (!use_glib) {
     sources -= [
       "message_loop/message_pump_glib.cc",