Implement ResizableIntArray.setLength and .get

This change revises ResizableIntArrayTests as well.
diff --git a/java/proguard.flags b/java/proguard.flags
index 1633522..1711b99 100644
--- a/java/proguard.flags
+++ b/java/proguard.flags
@@ -24,6 +24,10 @@
   *;
 }
 
+-keep class com.android.inputmethod.latin.ResizableIntArray {
+  *;
+}
+
 -keep class com.android.inputmethod.latin.spellcheck.SpellCheckerSettingsFragment {
   *;
 }