implement some APIs needed for OctoDroid

src/api-impl/android/text/TextUtils.java

@@ -62,7 +62,7 @@ public class TextUtils {
 	}
 
 	public static boolean isEmpty(CharSequence str) {
-		return str == null || str.equals("");
+		return str == null || str.length() == 0;
 	}
 
 	/**

src/api-impl/android/text/format/Formatter.java

@@ -0,0 +1,10 @@
+package android.text.format;
+
+import android.content.Context;
+
+public class Formatter {
+
+	public static String formatShortFileSize(Context context, long size) {
+		return String.valueOf(size);
+	}
+}