Dart VM: Simplify code generation for equality operators.

tests/standalone/debugger/step_in_equals_test.dart

+// Copyright (c) 2013, 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.
+
+import "debug_lib.dart";
+
+class MyClass {
+  operator ==(other) {
+    print(other);
+    return true;  // Breakpoint #3.
+  }
+}
+
+main() {
+  if (RunScript(testScript)) return;
+  var a = new MyClass();
+  var b = null;
+  var x = a == b;  // Breakpoint #1.
+  print(x);
+  b = 123;
+  a == b;  // Breakpoint #2.
+  print("after 2");
+  if (a == null) {  // Breakpoint #4.
+    throw "unreachable";
+  }
+  print("after 4");
+  if (null == a) {
+    throw "unreachable";
+  }
+  print("ok");
+}
+
+var testScript = [
+  MatchFrames(["main"]),
+  SetBreakpoint(18),
+  SetBreakpoint(21),
+  SetBreakpoint(10),
+  SetBreakpoint(23),
+  Resume(),
+  MatchFrames(["main"]),  // At breakpoint #1.
+  StepInto(),
+  MatchFrames(["main"]),  // Don't step into == method because of null.
+  Resume(),
+  MatchFrames(["main"]), // At breakpoint #2.
+  StepInto(),
+  StepInto(),
+  MatchFrames(["MyClass.==", "main"]),  // At MyClass.== entry.
+  Resume(),
+  MatchFrames(["MyClass.==", "main"]),  // At breakpoint #3.
+  Resume(),
+  MatchFrames(["main"]), // At breakpoint #4.
+  StepInto(),
+  MatchFrames(["main"]), // After breakpoint #4.
+  Step(),
+  MatchFrames(["main"]), // At null == a.
+  StepInto(),
+  MatchFrames(["main"]), // After null == a.
+  Resume()
+];