Define constants for ellipsize values

Also remove an already-done TODO item.

Test: bit CtsTextTestCases:*
Test: bit CtsWidgetTestCases:android.widget.cts.TextViewTest
Test: bit CtsWidgetTestCases:android.widget.cts.EditTextTest
Test: bit CtsWidgetTestCases:android.widget.cts.CheckedTextViewTest
Test: bit CtsWidgetTestCases:android.widget.cts.AutoCompleteTextViewTest
Test: bit CtsWidgetTestCases:android.widget.cts.MultiAutoCompleteTextViewTest
Test: adb shell am instrument -w -e package android.text com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I0c91ac3ad4ab5794c1e36f1f5e576d52acad66b2