bluetooth: Refactor (Add|Remove)Observer impls into BluetoothAdapter.

device/bluetooth/bluetooth_adapter_chromeos.cc

Index: device/bluetooth/bluetooth_adapter_chromeos.cc
diff --git a/device/bluetooth/bluetooth_adapter_chromeos.cc b/device/bluetooth/bluetooth_adapter_chromeos.cc
index b9cdd094128edae15f1a98b1cef3aaa0b9214c52..8f733238015dcc5e856fae0fc20b352d2e3fd070 100644
--- a/device/bluetooth/bluetooth_adapter_chromeos.cc
+++ b/device/bluetooth/bluetooth_adapter_chromeos.cc
@@ -144,18 +144,6 @@ void BluetoothAdapterChromeOS::DeleteOnCorrectThread() const {
     delete this;
 }
 
-void BluetoothAdapterChromeOS::AddObserver(
-    BluetoothAdapter::Observer* observer) {
-  DCHECK(observer);
-  observers_.AddObserver(observer);
-}
-
-void BluetoothAdapterChromeOS::RemoveObserver(
-    BluetoothAdapter::Observer* observer) {
-  DCHECK(observer);
-  observers_.RemoveObserver(observer);
-}
-
 std::string BluetoothAdapterChromeOS::GetAddress() const {
   if (!IsPresent())
     return std::string();