VM: Explicitly load function and context before calling a closure.

runtime/vm/flow_graph_compiler.h

Index: runtime/vm/flow_graph_compiler.h
===================================================================
--- runtime/vm/flow_graph_compiler.h	(revision 35546)
+++ runtime/vm/flow_graph_compiler.h	(working copy)
@@ -416,7 +416,9 @@
 
   Label* AddDeoptStub(intptr_t deopt_id, ICData::DeoptReasonId reason);
 
-  void AddDeoptIndexAtCall(intptr_t deopt_id, intptr_t token_pos);
+  void AddDeoptIndexAtCall(intptr_t deopt_id,
+                           intptr_t token_pos,
+                           intptr_t input_count = 0);
 
   void AddSlowPathCode(SlowPathCode* slow_path);
 
@@ -470,6 +472,7 @@
 
  private:
   friend class CheckStackOverflowSlowPath;  // For pending_deoptimization_env_.
+  friend class ClosureCallInstr;  // For pending_deoptimization_env_.
 
   void EmitFrameEntry();