Use custom drawable for Battery saver condition icon.

- Updated condition interface to use Drawable instead of Icon for icons.
- Converted all conditions to return drawable instead of Icon.
- Created a BatterySaverDrawable to draw a static battery saver icon.

Change-Id: Ie964f3439009c7658603a8ff352a05e964a0a795
Fixes: 76168403
Test: robotests

src/com/android/settings/dashboard/conditional/WorkModeCondition.java

@@ -19,7 +19,7 @@ package com.android.settings.dashboard.conditional;
 import android.content.Context;
 import android.content.Intent;
 import android.content.pm.UserInfo;
-import android.graphics.drawable.Icon;
+import android.graphics.drawable.Drawable;
 import android.os.UserHandle;
 import android.os.UserManager;
 
@@ -60,9 +60,8 @@ public class WorkModeCondition extends Condition {
     }
 
     @Override
-    public Icon getIcon() {
-        return Icon.createWithResource(mManager.getContext(),
-                R.drawable.ic_signal_workmode_enable);
+    public Drawable getIcon() {
+        return mManager.getContext().getDrawable(R.drawable.ic_signal_workmode_enable);
     }
 
     @Override