[debugger] fix debug-evaluate wrt shadowed context var.

test/cctest/test-debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5404 matching lines @@
     int source_line = GetSourceLineFromBreakEventMessage(print_buffer);
     CHECK(8 <= source_line && source_line <= 13);
     threaded_debugging_barriers.barrier_2.Wait();
   }
 }
 
 
 void V8Thread::Run() {
   const char* source =
       "flag = true;\n"
-      "function bar( new_value ) {\n"
-      "  flag = new_value;\n"
-      "  return \"Return from bar(\" + new_value + \")\";\n"
-      "}\n"
       "\n"
       "function foo() {\n"
       "  var x = 1;\n"
       "  while ( flag == true ) {\n"
       "    if ( x == 1 ) {\n"
       "      ThreadedAtBarrier1();\n"
       "    }\n"
       "    x = x + 1;\n"
       "  }\n"
       "}\n"
@@ skipping 22 matching lines @@
   }
   threaded_debugging_barriers.barrier_4.Wait();
   isolate_->Dispose();
 }
 
 
 void DebuggerThread::Run() {
   const int kBufSize = 1000;
   uint16_t buffer[kBufSize];
 
-  const char* command_1 = "{\"seq\":102,"
+  const char* command_1 =
+      "{\"seq\":102,"
       "\"type\":\"request\","
       "\"command\":\"evaluate\","
-      "\"arguments\":{\"expression\":\"bar(false)\"}}";
+      "\"arguments\":{\"expression\":\"flag = false\"}}";
   const char* command_2 = "{\"seq\":103,"
       "\"type\":\"request\","
       "\"command\":\"continue\"}";
 
   threaded_debugging_barriers.barrier_1.Wait();
   v8::Debug::DebugBreak(isolate_);
   threaded_debugging_barriers.barrier_2.Wait();
   v8::Debug::SendCommand(isolate_, buffer, AsciiToUtf16(command_1, buffer));
   v8::Debug::SendCommand(isolate_, buffer, AsciiToUtf16(command_2, buffer));
   threaded_debugging_barriers.barrier_4.Wait();
@@ skipping 2567 matching lines @@
   CompileRun("function foo() {}; foo();");
   --after_compile_handler_depth;
 }
 
 
 TEST(NoInterruptsInDebugListener) {
   DebugLocalContext env;
   v8::Debug::SetDebugEventListener(env->GetIsolate(), NoInterruptsOnDebugEvent);
   CompileRun("void(0);");
 }