Fixing a memory leak: activities are leaked.

TextLine was not fully cleared before recycling it which leads to
activity leaks if the activity happens: to register a text watcher.

bug:19045507

Change-Id: Ife0f7ce29865bd30ca2dfe8795023f51f275d659

core/java/android/text/TextLine.java

@@ -100,6 +100,9 @@ class TextLine {
         tl.mText = null;
         tl.mPaint = null;
         tl.mDirections = null;
+        tl.mSpanned = null;
+        tl.mTabs = null;
+        tl.mChars = null;
 
         tl.mMetricAffectingSpanSpanSet.recycle();
         tl.mCharacterStyleSpanSet.recycle();