Added memory pressure monitor for linux.

base/memory/memory_pressure_monitor_mac_unittest.cc

 // Copyright 2015 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.
 
-#include "base/memory/memory_pressure_monitor_mac.h"
+#include "base/memory/memory_pressure_monitor.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
-namespace mac {
 
 class TestMemoryPressureMonitor : public MemoryPressureMonitor {
  public:
   using MemoryPressureMonitor::MemoryPressureLevelForMacMemoryPressure;
 
   TestMemoryPressureMonitor() { }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TestMemoryPressureMonitor);
 };
@@ skipping 30 matching lines @@
   MemoryPressureListener::MemoryPressureLevel memory_pressure =
       monitor.GetCurrentPressureLevel();
   EXPECT_TRUE(memory_pressure ==
                   MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE ||
               memory_pressure ==
                   MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE ||
               memory_pressure ==
                   MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL);
 }
 
-}  // namespace mac
 }  // namespace base