log stack trace when finish() or onDestroy() is called

Some supurious calls to these functions when tests are still
running are observed. Add more logging to see what's the
caller.

Change-Id: I9254c3639bcb8619be39bfbc6981fae5bf5e7efa

Author: guang-google

tests/DumpRenderTree/src/com/android/dumprendertree/TestShellActivity.java

@@ -286,11 +286,23 @@ protected void onStop() {
         mWebView.stopLoading();
     }
 
+
+    //TODO: remove. this is temporary for bug investigation
+    @Override
+    public void finish() {
+      Exception e = new Exception("finish() call stack");
+      Log.d(LOGTAG, "finish stack trace", e);
+      super.finish();
+    }
+
     @Override
     protected void onDestroy() {
-        super.onDestroy();
+        //TODO: remove exception log. this is temporary for bug investigation
+        Exception e = new Exception("onDestroy stack trace");
+        Log.d(LOGTAG, "onDestroy stack trace", e);
         mWebView.destroy();
         mWebView = null;
+        super.onDestroy();
     }
 
     @Override