Debugger: do not reject data parsed in the background when debugging.

This has become possible since we never compile for debugging in the
first compile pass of a script.

R=vogelheim@chromium.org
BUG=chromium:513335
LOG=N

Review URL: https://codereview.chromium.org/1255153002

Cr-Commit-Position: refs/heads/master@{#29874}

src/compiler.cc

@@ -1379,8 +1379,8 @@ Handle<SharedFunctionInfo> Compiler::CompileStreamedScript(
 
   CompilationInfo compile_info(parse_info);
 
-  // If compiling for debugging, parse eagerly from scratch.
-  if (compile_info.is_debug()) parse_info->set_literal(NULL);
+  // The source was parsed lazily, so compiling for debugging is not possible.
+  DCHECK(!compile_info.is_debug());
 
   Handle<SharedFunctionInfo> result = CompileToplevel(&compile_info);
   if (!result.is_null()) isolate->debug()->OnAfterCompile(script);