MemoryPressureListener: fixes ref-counting.

base/memory/memory_pressure_listener.cc

Index: base/memory/memory_pressure_listener.cc
diff --git a/base/memory/memory_pressure_listener.cc b/base/memory/memory_pressure_listener.cc
index 911dbb38c89b86349f05aa392f4b4dfee56c3d88..e2ea106eaa60cf9ca5c43272400b23cae710ec02 100644
--- a/base/memory/memory_pressure_listener.cc
+++ b/base/memory/memory_pressure_listener.cc
@@ -9,9 +9,26 @@
 
 namespace {
 
-base::LazyInstance<ObserverListThreadSafe<base::MemoryPressureListener> >::Leaky
-    g_observers = LAZY_INSTANCE_INITIALIZER;
-
+// ObserverListThreadSafe is RefCountedThreadSafe, this traits is needed
+// to ensure the LazyInstance will hold a reference to it.
+struct LeakyLazyObserverListTraits :
+    base::internal::LeakyLazyInstanceTraits<
+        ObserverListThreadSafe<base::MemoryPressureListener> > {
+  static ObserverListThreadSafe<base::MemoryPressureListener>*
+      New(void* instance) {
+    ObserverListThreadSafe<base::MemoryPressureListener>* ret =
+        base::internal::LeakyLazyInstanceTraits<
+            ObserverListThreadSafe<base::MemoryPressureListener> >::New(
+                instance);
+    // Leaky.
+    ret->AddRef();
+    return ret;
+  }
+};
+
+base::LazyInstance<
+    ObserverListThreadSafe<base::MemoryPressureListener>,
+    LeakyLazyObserverListTraits> g_observers = LAZY_INSTANCE_INITIALIZER;
 }  // namespace
 
 namespace base {