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

lib/compiler/implementation/ssa/codegen.dart

Index: lib/compiler/implementation/ssa/codegen.dart
diff --git a/lib/compiler/implementation/ssa/codegen.dart b/lib/compiler/implementation/ssa/codegen.dart
index c5db189ba064fee8815acab54e21ba4825b7f141..df545511e8a36f4336fa1ce8e3f9e2d999ecbce3 100644
--- a/lib/compiler/implementation/ssa/codegen.dart
+++ b/lib/compiler/implementation/ssa/codegen.dart
@@ -241,6 +241,11 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
       breakAction = new Map<Element, ElementAction>(),
       continueAction = new Map<Element, ElementAction>(),
       unsignedShiftPrecedences = JSPrecedence.binary['>>>'] {
+
+    Interceptors interceptors = backend.builder.interceptors;
+    equalsNullElement = interceptors.getEqualsNullInterceptor();
+    boolifiedEqualsNullElement =
+        interceptors.getBoolifiedVersionOf(equalsNullElement);
   }
 
   abstract visitTypeGuard(HTypeGuard node);
@@ -1260,6 +1265,14 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
   visitEquals(HEquals node) {
     if (node.builtin) {
       emitIdentityComparison(node.left, node.right);
+    } else if (node.element === equalsNullElement ||
+               node.element === boolifiedEqualsNullElement) {
+      beginExpression(JSPrecedence.CALL_PRECEDENCE);
+      use(node.target, JSPrecedence.CALL_PRECEDENCE);
+      buffer.add('(');
+      use(node.left, JSPrecedence.ASSIGNMENT_PRECEDENCE);
+      buffer.add(')');
+      endExpression(JSPrecedence.CALL_PRECEDENCE);
     } else {
       visitInvokeStatic(node);
     }