Replace more ObserverList with base::ObserverList.

chromeos/accelerometer/accelerometer_reader.cc

Index: chromeos/accelerometer/accelerometer_reader.cc
diff --git a/chromeos/accelerometer/accelerometer_reader.cc b/chromeos/accelerometer/accelerometer_reader.cc
index fe8422c1ca6ec0965361c6a8a379858538f0d9f8..a89cdd6ea55376f4742626844a95fff7eb227517 100644
--- a/chromeos/accelerometer/accelerometer_reader.cc
+++ b/chromeos/accelerometer/accelerometer_reader.cc
@@ -212,7 +212,7 @@ void AccelerometerReader::RemoveObserver(Observer* observer) {
 
 AccelerometerReader::AccelerometerReader()
     : configuration_(new AccelerometerReader::Configuration()),
-      observers_(new ObserverListThreadSafe<Observer>()),
+      observers_(new base::ObserverListThreadSafe<Observer>()),
       weak_factory_(this) {
 }