Adding flag to specify the used memory pressure strategy

base/chromeos/memory_pressure_observer_chromeos_unittest.cc

Index: base/chromeos/memory_pressure_observer_chromeos_unittest.cc
diff --git a/base/chromeos/memory_pressure_observer_chromeos_unittest.cc b/base/chromeos/memory_pressure_observer_chromeos_unittest.cc
index 8b28957c7e32751235569d6900b39833de783da0..a227f93dc0e79ad49814b3f43fff3bfbfdf04533 100644
--- a/base/chromeos/memory_pressure_observer_chromeos_unittest.cc
+++ b/base/chromeos/memory_pressure_observer_chromeos_unittest.cc
@@ -42,7 +42,10 @@ bool WasOnMemoryPressureCalled() {
 
 class TestMemoryPressureObserver : public MemoryPressureObserverChromeOS {
  public:
-  TestMemoryPressureObserver() : memory_in_percent_override_(0) {
+  TestMemoryPressureObserver() :
+    MemoryPressureObserverChromeOS(
+        MemoryPressureObserverChromeOS::THRESHOLD_DEFAULT),
+    memory_in_percent_override_(0) {
     // Disable any timers which are going on and set a special memory reporting
     // function.
     StopObserving();