Preserve exception message in iterator finalization.

src/compiler/ast-graph-builder.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/ast-graph-builder.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
@@ skipping 1424 matching lines @@
   try_control.BeginTry();
   {
     ControlScopeForCatch scope(this, &try_control);
     STATIC_ASSERT(TryBlockConstant::kElementCount == 1);
     environment()->Push(current_context());
     Visit(stmt->try_block());
     environment()->Pop();
   }
   try_control.EndTry();
 
-  // Clear message object as we enter the catch block.
-  Node* the_hole = jsgraph()->TheHoleConstant();
-  NewNode(javascript()->StoreMessage(), the_hole);
+  // If requested, clear message object as we enter the catch block.
+  if (stmt->clear_pending_message()) {
+    Node* the_hole = jsgraph()->TheHoleConstant();
+    NewNode(javascript()->StoreMessage(), the_hole);
+  }
 
   // Create a catch scope that binds the exception.
   Node* exception = try_control.GetExceptionNode();
   Handle<String> name = stmt->variable()->name();
   const Operator* op = javascript()->CreateCatchContext(name);
   Node* context = NewNode(op, exception, GetFunctionClosureForContext());
 
   // Evaluate the catch-block.
   VisitInScope(stmt->catch_block(), stmt->scope(), context);
   try_control.EndCatch();
@@ skipping 2909 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8