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

runtime/vm/flow_graph_compiler.h

Index: runtime/vm/flow_graph_compiler.h
===================================================================
--- runtime/vm/flow_graph_compiler.h	(revision 35455)
+++ runtime/vm/flow_graph_compiler.h	(working copy)
@@ -110,7 +110,7 @@
 class CompilerDeoptInfo : public ZoneAllocated {
  public:
   CompilerDeoptInfo(intptr_t deopt_id,
-                    DeoptReasonId reason,
+                    ICData::DeoptReasonId reason,
                     Environment* deopt_env)
       : pc_offset_(-1),
         deopt_id_(deopt_id),
@@ -131,7 +131,7 @@
   void set_pc_offset(intptr_t offset) { pc_offset_ = offset; }
 
   intptr_t deopt_id() const { return deopt_id_; }
-  DeoptReasonId reason() const { return reason_; }
+  ICData::DeoptReasonId reason() const { return reason_; }
   const Environment* deopt_env() const { return deopt_env_; }
 
  private:
@@ -142,7 +142,7 @@
 
   intptr_t pc_offset_;
   const intptr_t deopt_id_;
-  const DeoptReasonId reason_;
+  const ICData::DeoptReasonId reason_;
   Environment* deopt_env_;
 
   DISALLOW_COPY_AND_ASSIGN(CompilerDeoptInfo);
@@ -152,10 +152,10 @@
 class CompilerDeoptInfoWithStub : public CompilerDeoptInfo {
  public:
   CompilerDeoptInfoWithStub(intptr_t deopt_id,
-                            DeoptReasonId reason,
+                            ICData::DeoptReasonId reason,
                             Environment* deopt_env)
       : CompilerDeoptInfo(deopt_id, reason, deopt_env), entry_label_() {
-    ASSERT(reason != kDeoptAtCall);
+    ASSERT(reason != ICData::kDeoptAtCall);
   }
 
   Label* entry_label() { return &entry_label_; }
@@ -414,7 +414,7 @@
 
   void RecordSafepoint(LocationSummary* locs);
 
-  Label* AddDeoptStub(intptr_t deopt_id, DeoptReasonId reason);
+  Label* AddDeoptStub(intptr_t deopt_id, ICData::DeoptReasonId reason);
 
   void AddDeoptIndexAtCall(intptr_t deopt_id, intptr_t token_pos);