Revert all the changes to equals operator. Causing buildbot trouble.

lib/compiler/implementation/ssa/optimize.dart

Index: lib/compiler/implementation/ssa/optimize.dart
diff --git a/lib/compiler/implementation/ssa/optimize.dart b/lib/compiler/implementation/ssa/optimize.dart
index 664b62bd63cdcce93493fbe7bad40f8518d6e4bf..3d67053bbedc0dd1db47536eff3eb6c13ad5f2c9 100644
--- a/lib/compiler/implementation/ssa/optimize.dart
+++ b/lib/compiler/implementation/ssa/optimize.dart
@@ -460,6 +460,28 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
     if (right.isConstantNull()) {
       if (left.propagatedType.isPrimitive()) {
         return graph.addConstantBool(false);
+      } else {
+        // TODO(floitsch): cache interceptors.
+        Interceptors interceptors = backend.builder.interceptors;
+        Element equalsElement = interceptors.getEqualsInterceptor();
+        // If we have a different element than [equalsElement], we
+        // don't need to optimize this instruction to use another
+        // element: we know the element is either eqNull or eqNullB.
+        if (node.element === equalsElement) {
+          Element targetElement = interceptors.getEqualsNullInterceptor();
+          bool onlyUsedInBoolify = allUsersAreBoolifies(node);
+          if (onlyUsedInBoolify) {
+            targetElement = interceptors.getBoolifiedVersionOf(targetElement);
+          }
+          HStatic target = new HStatic(targetElement);
+          node.block.addBefore(node, target);
+          HEquals result = new HEquals(target, node.left, node.right);
+          if (onlyUsedInBoolify) {
+            result.usesBoolifiedInterceptor = true;
+            result.propagatedType = HType.BOOLEAN;
+          }
+          return result;
+        }
       }
     }