Make memory pressure notifier configurable

base/memory/memory_pressure_monitor_chromeos.cc

Index: base/memory/memory_pressure_monitor_chromeos.cc
diff --git a/base/memory/memory_pressure_monitor_chromeos.cc b/base/memory/memory_pressure_monitor_chromeos.cc
index 2d0b0a62fc6d7c1dbbb77aa98f06132d5f93a966..8880d1620b14e7bbc793cb3c8e068d9a6c79a835 100644
--- a/base/memory/memory_pressure_monitor_chromeos.cc
+++ b/base/memory/memory_pressure_monitor_chromeos.cc
@@ -230,7 +230,7 @@ void MemoryPressureMonitor::CheckMemoryPressure() {
     return;
   }
   moderate_pressure_repeat_count_ = 0;
-  MemoryPressureListener::NotifyMemoryPressure(current_memory_pressure_level_);
+  dispatch_callback_(current_memory_pressure_level_);
 }
 
 // Gets the used ChromeOS memory in percent.
@@ -271,5 +271,9 @@ int MemoryPressureMonitor::GetUsedMemoryInPercent() {
   return percentage;
 }
 
+void MemoryPressureMonitor::SetDispatchCallback(DispatchCallback callback) {
+  dispatch_callback_ = callback;
+}
+
 }  // namespace chromeos
 }  // namespace base