Get the default device scale factor from monitor

ash/monitor/multi_monitor_manager.cc

Index: ash/monitor/multi_monitor_manager.cc
diff --git a/ash/monitor/multi_monitor_manager.cc b/ash/monitor/multi_monitor_manager.cc
index 874f22408018b9891e0c04315312e5c451b3781b..c9c2fb38bdd2ed15996b98c25e98e676ea483727 100644
--- a/ash/monitor/multi_monitor_manager.cc
+++ b/ash/monitor/multi_monitor_manager.cc
@@ -169,10 +169,12 @@ void MultiMonitorManager::Init() {
   base::SplitString(size_str, ',', &parts);
   for (vector<string>::const_iterator iter = parts.begin();
        iter != parts.end(); ++iter) {
-    monitors_.push_back(CreateMonitorFromSpec(*iter));
+    monitors_.push_back(CreateMonitorFromSpec(
+        default_device_scale_factor(), *iter));
   }
   if (monitors_.empty())
-    monitors_.push_back(CreateMonitorFromSpec("" /* default */));
+    monitors_.push_back(CreateMonitorFromSpec(
+        default_device_scale_factor(), "" /* default */));
 }
 
 void MultiMonitorManager::AddRemoveMonitorImpl() {
@@ -185,7 +187,8 @@ void MultiMonitorManager::AddRemoveMonitorImpl() {
   } else {
     // Add if there is only one monitor.
     new_monitors.push_back(monitors_[0]);
-    new_monitors.push_back(CreateMonitorFromSpec("50+50-1280x768"));
+    new_monitors.push_back(CreateMonitorFromSpec(
+        default_device_scale_factor(), "50+50-1280x768"));
   }
   if (new_monitors.size())
     OnNativeMonitorsChanged(new_monitors);