Optimize equality for case when all targets are Object.equals.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
===================================================================
--- runtime/vm/intermediate_language.h	(revision 10581)
+++ runtime/vm/intermediate_language.h	(working copy)
@@ -674,7 +674,7 @@
       : ComparisonComp(kind, left, right),
         token_pos_(token_pos),
         try_index_(try_index),
-        receiver_class_id_(kObjectCid) {
+        receiver_class_id_(kIllegalCid) {
     ASSERT((kind == Token::kEQ) || (kind == Token::kNE));
   }
 
@@ -683,8 +683,10 @@
   intptr_t token_pos() const { return token_pos_; }
   intptr_t try_index() const { return try_index_; }
 
+  // Receiver class id is computed from collected ICData.
   void set_receiver_class_id(intptr_t value) { receiver_class_id_ = value; }
   intptr_t receiver_class_id() const { return receiver_class_id_; }
+
   virtual void PrintOperandsTo(BufferFormatter* f) const;
 
   virtual bool CanDeoptimize() const { return true; }
@@ -708,7 +710,7 @@
       : ComparisonComp(kind, left, right),
         token_pos_(token_pos),
         try_index_(try_index),
-        operands_class_id_(kObjectCid) {
+        operands_class_id_(kIllegalCid) {
     ASSERT(Token::IsRelationalOperator(kind));
   }