Move StringUtils under common.

Bug: 18108776
Change-Id: Ia46a4102a0e86e71118ca5e641f9f531998e166b
diff --git a/tools/dicttool/Android.mk b/tools/dicttool/Android.mk
index 09af9a0..90be411 100644
--- a/tools/dicttool/Android.mk
+++ b/tools/dicttool/Android.mk
@@ -60,8 +60,7 @@
         latin/utils/FileUtils.java \
         latin/utils/JniUtils.java \
         latin/utils/LocaleUtils.java \
-        latin/utils/ResizableIntArray.java \
-        latin/utils/StringUtils.java
+        latin/utils/ResizableIntArray.java
 
 LATINIME_OVERRIDABLE_SRC_FILES_FOR_DICTTOOL := \
         latin/define/DebugFlags.java