Added memory pressure monitor for linux.

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index 203400ea7757b12c8581abdb4556a2f1bca2f863..fceaeec4cd3d7783e2b6f618e55868140799a8a5 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -128,6 +128,10 @@
 #include <glib-object.h>
 #endif
 
+#if defined(OS_LINUX)
+#include "base/memory/memory_pressure_monitor_linux.h"
+#endif
+
 #if defined(OS_LINUX) && defined(USE_UDEV)
 #include "content/browser/device_monitor_udev.h"
 #elif defined(OS_MACOSX) && !defined(OS_IOS)
@@ -664,6 +668,8 @@ int BrowserMainLoop::PreCreateThreads() {
     memory_pressure_monitor_.reset(new base::chromeos::MemoryPressureMonitor(
         chromeos::switches::GetMemoryPressureThresholds()));
   }
+#elif defined(OS_LINUX)
+  memory_pressure_monitor_.reset(new base::nix::MemoryPressureMonitor());
 #elif defined(OS_MACOSX) && !defined(OS_IOS)
   memory_pressure_monitor_.reset(new base::mac::MemoryPressureMonitor());
 #elif defined(OS_WIN)