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

runtime/vm/code_descriptors.h

 // Copyright (c) 2012, 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.
 
 #ifndef VM_CODE_DESCRIPTORS_H_
 #define VM_CODE_DESCRIPTORS_H_
 
 #include "vm/ast.h"
 #include "vm/code_generator.h"
 #include "vm/globals.h"
 #include "vm/growable_array.h"
 #include "vm/object.h"
 
 namespace dart {
 
 class DescriptorList : public ZoneAllocated {
  public:
   struct PcDesc {
     intptr_t pc_offset;        // PC offset value of the descriptor.
     PcDescriptors::Kind kind;  // Descriptor kind (kDeopt, kOther).
     intptr_t deopt_id;         // Deoptimization id.
-    intptr_t data;             // Token position or deopt rason.
+    intptr_t data;             // Token position or deopt reason.
     intptr_t try_index;        // Try block index of PC or deopt array index.
     void SetTokenPos(intptr_t value) { data = value; }
     intptr_t TokenPos() const { return data; }
-    void SetDeoptReason(DeoptReasonId value) { data = value; }
-    DeoptReasonId DeoptReason() const {
-      return static_cast<DeoptReasonId>(data);
+    void SetDeoptReason(ICData::DeoptReasonId value) { data = value; }
+    ICData::DeoptReasonId DeoptReason() const {
+      ASSERT((0 <= data) && (data < ICData::ICData::kDeoptNumReasons));
+      return static_cast<ICData::DeoptReasonId>(data);
     }
   };
 
   explicit DescriptorList(intptr_t initial_capacity) : list_(initial_capacity) {
   }
   ~DescriptorList() { }
 
   intptr_t Length() const {
     return list_.length();
   }
 
   intptr_t PcOffset(intptr_t index) const {
     return list_[index].pc_offset;
   }
   PcDescriptors::Kind Kind(intptr_t index) const {
     return list_[index].kind;
   }
   intptr_t DeoptId(intptr_t index) const {
     return list_[index].deopt_id;
   }
   intptr_t TokenPos(intptr_t index) const {
     return list_[index].TokenPos();
   }
-  DeoptReasonId DeoptReason(intptr_t index) const {
+  ICData::DeoptReasonId DeoptReason(intptr_t index) const {
     return list_[index].DeoptReason();
   }
   intptr_t TryIndex(intptr_t index) const {
     return list_[index].try_index;
   }
 
   void AddDescriptor(PcDescriptors::Kind kind,
                      intptr_t pc_offset,
                      intptr_t deopt_id,
                      intptr_t token_index,
@@ skipping 114 matching lines @@
   }
 
  private:
   GrowableArray<struct HandlerDesc> list_;
   DISALLOW_COPY_AND_ASSIGN(ExceptionHandlerList);
 };
 
 }  // namespace dart
 
 #endif  // VM_CODE_DESCRIPTORS_H_