Preserve exception message in iterator finalization.

src/interpreter/bytecode-generator.cc

 // Copyright 2015 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/interpreter/bytecode-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-register-allocator.h"
 #include "src/interpreter/control-flow-builders.h"
@@ skipping 1181 matching lines @@
   {
     ControlScopeForTryCatch scope(this, &try_control_builder);
     Visit(stmt->try_block());
   }
   try_control_builder.EndTry();
 
   // Create a catch scope that binds the exception.
   VisitNewLocalCatchContext(stmt->variable());
   builder()->StoreAccumulatorInRegister(context);
 
-  // Clear message object as we enter the catch block.
-  builder()->CallRuntime(Runtime::kInterpreterClearPendingMessage, no_reg, 0);
+  // If requested, clear message object as we enter the catch block.
+  if (stmt->clear_pending_message()) {
+    builder()->CallRuntime(Runtime::kInterpreterClearPendingMessage, no_reg, 0);
+  }
 
   // Load the catch context into the accumulator.
   builder()->LoadAccumulatorWithRegister(context);
 
   // Evaluate the catch-block.
   VisitInScope(stmt->catch_block(), stmt->scope());
   try_control_builder.EndCatch();
 }
 
 
@@ skipping 1933 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8