Remember all deopt reasons in ic_data, not just the last one.

runtime/vm/intermediate_language_x64.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_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 4988 matching lines @@
 }
 
 
 void PolymorphicInstanceCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Label* deopt = compiler->AddDeoptStub(deopt_id(),
                                         kDeoptPolymorphicInstanceCallTestFail);
   if (ic_data().NumberOfChecks() == 0) {
     __ jmp(deopt);
     return;
   }
-  ASSERT(ic_data().num_args_tested() == 1);
+  ASSERT(ic_data().NumArgsTested() == 1);
   if (!with_checks()) {
     ASSERT(ic_data().HasOneTarget());
     const Function& target = Function::ZoneHandle(ic_data().GetTargetAt(0));
     compiler->GenerateStaticCall(deopt_id(),
                                  instance_call()->token_pos(),
                                  target,
                                  instance_call()->ArgumentCount(),
                                  instance_call()->argument_names(),
                                  locs());
     return;
@@ skipping 478 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64