Reset drag accelerator state in Editor#sendOnTextChanged.

This fixes a crash that happened because mStartOffset
could point to an invalid offset after changing the text.

Bug: 21178876
Change-Id: I2fbb5ea3d6b8c5a97ca7248116b58ead673a8b0a

core/java/android/widget/Editor.java

@@ -1162,6 +1162,10 @@ public class Editor {
         // We do not hide the span controllers, since they can be added when a new text is
         // inserted into the text view (voice IME).
         hideCursorControllers();
+        // Reset drag accelerator.
+        if (mSelectionModifierCursorController != null) {
+            mSelectionModifierCursorController.resetTouchOffsets();
+        }
         stopTextActionMode();
     }