Add a finch experiment for different memory pressure management strategies in ChromeOS.

base/chromeos/memory_pressure_observer_chromeos.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_CHROMEOS_MEMORY_PRESSURE_OBSERVER_CHROMEOS_H_
 #define BASE_CHROMEOS_MEMORY_PRESSURE_OBSERVER_CHROMEOS_H_
 
 #include "base/base_export.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
@@ skipping 32 matching lines @@
     THRESHOLD_AGGRESSIVE_CACHE_DISCARD = 2,
     // Discard tabs earlier, allowing the system to get faster.
     THRESHOLD_AGGRESSIVE_TAB_DISCARD = 3,
     // Discard caches and tabs earlier to allow the system to be faster.
     THRESHOLD_AGGRESSIVE = 4
   };
 
   explicit MemoryPressureObserverChromeOS(MemoryPressureThresholds thresholds);
   virtual ~MemoryPressureObserverChromeOS();
 
+  // Return the memory pressure management threshold. Controlled by a flag and
+  // FieldTrial.

[Mr4D (OOO till 08-26), 2015/02/06 03:56:35]

Not here.

+  static MemoryPressureThresholds GetMemoryPressureThresholds();
+
   // Redo the memory pressure calculation soon and call again if a critical
   // memory pressure prevails. Note that this call will trigger an asynchronous
   // action which gives the system time to release memory back into the pool.
   void ScheduleEarlyCheck();
 
   // Get the current memory pressure level.
   base::MemoryPressureListener::MemoryPressureLevel GetCurrentPressureLevel() {
     return current_memory_pressure_level_;
   }
 
@@ skipping 37 matching lines @@
   const int critical_pressure_threshold_percent_;
 
   base::WeakPtrFactory<MemoryPressureObserverChromeOS> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryPressureObserverChromeOS);
 };
 
 }  // namespace base
 
 #endif  // BASE_CHROMEOS_MEMORY_PRESSURE_OBSERVER_CHROMEOS_H_