[debugger] Prevent shared function info duplicates

Clear the list of shared function infos attached to a script before
compiling for live edit in order to avoid duplicates. This was lost in
058deb27. Additionally, we restore the
original list of shared function infos once we're done with live edit
work.

R=yangguo@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/1969293003
Cr-Commit-Position: refs/heads/master@{#36200}

src/compiler.cc

@@ -1217,6 +1217,12 @@ bool Compiler::CompileForLiveEdit(Handle<Script> script) {
   Isolate* isolate = script->GetIsolate();
   DCHECK(AllowCompilation::IsAllowed(isolate));
 
+  // In order to ensure that live edit function info collection finds the newly
+  // generated shared function infos, clear the script's list temporarily
+  // and restore it at the end of this method.
+  Handle<Object> old_function_infos(script->shared_function_infos(), isolate);
+  script->set_shared_function_infos(Smi::FromInt(0));
+
   // Start a compilation.
   Zone zone(isolate->allocator());
   ParseInfo parse_info(&zone, script);
@@ -1224,13 +1230,21 @@ bool Compiler::CompileForLiveEdit(Handle<Script> script) {
   parse_info.set_global();
   info.MarkAsDebug();
   // TODO(635): support extensions.
-  if (CompileToplevel(&info).is_null()) {
+  const bool compilation_succeeded = !CompileToplevel(&info).is_null();
+
+  // Restore the original function info list in order to remain side-effect
+  // free as much as possible, since some code expects the old shared function
+  // infos to stick around.
+  script->set_shared_function_infos(*old_function_infos);
+
+  if (!compilation_succeeded) {
     return false;
   }
 
   // Check postconditions on success.
   DCHECK(!isolate->has_pending_exception());
-  return true;
+
+  return compilation_succeeded;
 }
 
 // TODO(turbofan): In the future, unoptimized code with deopt support could