Add javascript compatibility warnings for strings that are not identical, but

runtime/vm/flow_graph_compiler.cc

 // 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.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/cha.h"
 #include "vm/dart_entry.h"
@@ skipping 874 matching lines @@
 
 void FlowGraphCompiler::GenerateStaticCall(intptr_t deopt_id,
                                            intptr_t token_pos,
                                            const Function& function,
                                            intptr_t argument_count,
                                            const Array& argument_names,
                                            LocationSummary* locs) {
   const Array& arguments_descriptor =
       Array::ZoneHandle(ArgumentsDescriptor::New(argument_count,
                                                  argument_names));
-  if (is_optimizing()) {
+  // Proper reporting of Javascript incompatibilities requires icdata and
+  // may therefore prevent the optimization of some static calls.
+  if (is_optimizing() &&
+      !(FLAG_warn_on_javascript_compatibility &&
+        (MethodRecognizer::RecognizeKind(function) ==
+         MethodRecognizer::kObjectIdentical))) {
     EmitOptimizedStaticCall(function, arguments_descriptor, argument_count,
                             deopt_id, token_pos, locs);
   } else {
     EmitUnoptimizedStaticCall(function, arguments_descriptor, argument_count,
                               deopt_id, token_pos, locs);
   }
 }
 
 
 void FlowGraphCompiler::GenerateNumberTypeCheck(Register kClassIdReg,
@@ skipping 397 matching lines @@
 
   for (int i = 0; i < len; i++) {
     sorted->Add(CidTarget(ic_data.GetReceiverClassIdAt(i),
                           &Function::ZoneHandle(ic_data.GetTargetAt(i)),
                           ic_data.GetCountAt(i)));
   }
   sorted->Sort(HighestCountFirst);
 }
 
 }  // namespace dart