Adding flag to specify the used memory pressure strategy

base/chromeos/memory_pressure_observer_chromeos.h

Index: base/chromeos/memory_pressure_observer_chromeos.h
diff --git a/base/chromeos/memory_pressure_observer_chromeos.h b/base/chromeos/memory_pressure_observer_chromeos.h
index 23b6b3450d8cf2f9ef7f907be1aab144b69ff58f..d543036305ba4ce8bad247ab94792861a8f58863 100644
--- a/base/chromeos/memory_pressure_observer_chromeos.h
+++ b/base/chromeos/memory_pressure_observer_chromeos.h
@@ -27,7 +27,15 @@ class BASE_EXPORT MemoryPressureObserverChromeOS {
  public:
   using GetUsedMemoryInPercentCallback = int (*)();
 
-  MemoryPressureObserverChromeOS();
+  enum MemoryPressureThresholds {
+    DEFAULT_THRESHOLDS = 0,             // Use the default.

[Charlie Reis, 2015/01/21 17:42:05]

These names and comments are confusing to me.  Normal, aggressive, moderate, and
critical could all be names on the same scale, so please add a comment
explaining how they relate.

Also, I'm not sure about the conventions in this code, but the content module
tends to name enums differently:
http://www.chromium.org/developers/content-module/content-api
"enum values should start with the name of the type, i.e. PAGE_TRANSITION_LINK
in the content::PageTransition enum"

[Mr4D (OOO till 08-26), 2015/01/21 18:52:14]

Done.

+    NORMAL_THRESHOLDS = 1,              // Use both thresholds as normal.
+    AGGRESSIVE_MODERATE_THRESHOLD = 2,  // Use an aggressive moderate threshold.
+    AGGRESSIVE_CRITICAL_THRESHOLD = 3,  // Use an aggressive critical threshold.
+    AGGRESSIVE_THRESHOLDS = 4           // Both thresholds are aggressive.
+  };
+
+  explicit MemoryPressureObserverChromeOS(MemoryPressureThresholds thresholds);
   virtual ~MemoryPressureObserverChromeOS();
 
   // Redo the memory pressure calculation soon and call again if a critical
@@ -71,6 +79,10 @@ class BASE_EXPORT MemoryPressureObserverChromeOS {
   // gets used to count the number of events since the last event occured.
   int moderate_pressure_repeat_count_;
 
+  // The thresholds for moderate and critical pressure.
+  const int moderate_pressure_threshold_;
+  const int critical_pressure_threshold_;
+
   base::WeakPtrFactory<MemoryPressureObserverChromeOS> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryPressureObserverChromeOS);