Reland "Recognize and optimize a.runtimeType == b.runtimeType pattern."

runtime/vm/precompiler.h

Index: runtime/vm/precompiler.h
diff --git a/runtime/vm/precompiler.h b/runtime/vm/precompiler.h
index e10247c466a022f57a9d4811e6e6a2761b96dd31..f3a8d02f6a881cf9c0312a4b28ad640912e59fe3 100644
--- a/runtime/vm/precompiler.h
+++ b/runtime/vm/precompiler.h
@@ -356,7 +356,8 @@ class Precompiler : public ValueObject {
       Dart_QualifiedFunctionName embedder_entry_points[],
       bool reset_fields);
 
-  static RawError* CompileFunction(Thread* thread,
+  static RawError* CompileFunction(Precompiler* precompiler,
+                                   Thread* thread,
                                    Zone* zone,
                                    const Function& function,
                                    FieldTypeMap* field_type_map = NULL);
@@ -367,6 +368,15 @@ class Precompiler : public ValueObject {
   static RawFunction* CompileStaticInitializer(const Field& field,
                                                bool compute_type);
 
+  // Returns true if get:runtimeType is not overloaded by any class.
+  bool get_runtime_type_is_unique() const {
+    return get_runtime_type_is_unique_;
+  }
+
+  FieldTypeMap* field_type_map() {
+    return &field_type_map_;
+  }
+
  private:
   Precompiler(Thread* thread, bool reset_fields);
 
@@ -466,6 +476,8 @@ class Precompiler : public ValueObject {
   InstanceSet consts_to_retain_;
   FieldTypeMap field_type_map_;
   Error& error_;
+
+  bool get_runtime_type_is_unique_;
 };