Add regression test for null check elimination.

Prompted by
    https://android-review.googlesource.com/110090

Bug: 17969907
Change-Id: I938c27cda0681b9431d69baf4eafa7ca2f9b5c9c
diff --git a/test/083-compiler-regressions/src/Main.java b/test/083-compiler-regressions/src/Main.java
index 8d7bf01..9c772b9 100644
--- a/test/083-compiler-regressions/src/Main.java
+++ b/test/083-compiler-regressions/src/Main.java
@@ -38,6 +38,7 @@
         b13679511Test();
         b16177324TestWrapper();
         b16230771TestWrapper();
+        b17969907TestWrapper();
         largeFrameTest();
         largeFrameTestFloat();
         mulBy1Test();
@@ -977,6 +978,24 @@
       }
     }
 
+    static void b17969907TestWrapper() {
+      try {
+        b17969907Test();
+        System.out.println("b17969907Test unexpectedly didn't throw NPE.");
+      } catch (NullPointerException expected) {
+        System.out.println("b17969907TestWrapper caught NPE as expected.");
+      }
+    }
+
+    public static void b17969907Test() {
+      Integer i = new Integer(1);
+      int sum = 0;
+      while (sum < 100) {
+        sum += i;
+        i = null;
+      }
+    }
+
     static double TooManyArgs(
           long l00,
           long l01,