DBC: Fix not-stopping/crashing at fast Smi op breakpoints.

runtime/observatory/tests/service/breakpoint_two_args_checked_test.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// VMOptions=--error_on_bad_type --error_on_bad_override  --verbose_debug
+
+// This test is mostly interesting for DBC, which needs to patch two bytecodes
+// to create a breakpoint for fast Smi ops.
+
+import 'package:observatory/service_io.dart';
+import 'package:unittest/unittest.dart';
+import 'service_test_common.dart';
+import 'test_helper.dart';
+import 'dart:developer';
+
+const int LINE_A = 26;
+const int LINE_B = 27;
+const int LINE_C = 28;
+
+class NotGeneric { }
+
+testeeMain() {
+  var x = new List(1);
+  var y = 7;
+  debugger();
+  print("Statement");
+  x[0] = 3;         // Line A.
+  x is NotGeneric;  // Line B.
+  y & 4;            // Line C.
+}
+
+var tests = [
+
+hasStoppedAtBreakpoint,
+
+// Add breakpoints.
+(Isolate isolate) async {
+  var rootLib = await isolate.rootLibrary.load();
+  var script = rootLib.scripts[0];
+
+  var bpt1 = await isolate.addBreakpoint(script, LINE_A);
+  print(bpt1);
+  expect(bpt1.resolved, isTrue);
+  expect(await bpt1.location.getLine(), equals(LINE_A));
+
+  var bpt2 = await isolate.addBreakpoint(script, LINE_B);
+  print(bpt2);
+  expect(bpt2.resolved, isTrue);
+  expect(await bpt2.location.getLine(), equals(LINE_B));
+
+  var bpt3 = await isolate.addBreakpoint(script, LINE_C);
+  print(bpt3);
+  expect(bpt3.resolved, isTrue);
+  expect(await bpt3.location.getLine(), equals(LINE_C));
+},
+
+resumeIsolate,
+
+hasStoppedAtBreakpoint,
+stoppedAtLine(LINE_A),
+resumeIsolate,
+
+hasStoppedAtBreakpoint,
+stoppedAtLine(LINE_B),
+resumeIsolate,
+
+hasStoppedAtBreakpoint,
+stoppedAtLine(LINE_C),
+resumeIsolate,
+
+];
+
+main(args) => runIsolateTests(args, tests, testeeConcurrent: testeeMain);