Reland "[debugger] Expose reference to the function in debug-evaluate"

This is a reland of 8de427fa

Original change's description:
> [debugger] Expose reference to the function in debug-evaluate
>
> R=verwaest@chromium.org
>
> Bug: chromium:878723
> Change-Id: Ic07f75f15230018b6d19cd1ee21f4be6dcad6360
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1667408
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Commit-Queue: Yang Guo <yangguo@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#62385}

TBR=jgruber@chromium.org

Bug: chromium:878723
Change-Id: I0386655a9b2632d2d9438e674d4205ce5e5365f5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1679490Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62401}

src/debug/debug-scopes.cc

@@ -624,6 +624,16 @@ bool ScopeIterator::VisitLocals(const Visitor& visitor, Mode mode) const {
     if (visitor(isolate_->factory()->this_string(), receiver)) return true;
   }
 
+  if (current_scope_->is_function_scope()) {
+    Variable* function_var =
+        current_scope_->AsDeclarationScope()->function_var();
+    if (function_var != nullptr) {
+      Handle<JSFunction> function = frame_inspector_->GetFunction();
+      Handle<String> name = function_var->name();
+      if (visitor(name, function)) return true;
+    }
+  }
+
   for (Variable* var : *current_scope_->locals()) {
     DCHECK(!var->is_this());
     if (ScopeInfo::VariableIsSynthetic(*var->name())) continue;

test/debugger/debug/debug-evaluate-function-var.js

+// Copyright 2019 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.
+
+Debug = debug.Debug
+var exception = null;
+
+function listener(event, exec_state, event_data, data) {
+  try {
+    if (event == Debug.DebugEvent.Break) {
+      var frame = exec_state.frame(0);
+      try {
+        assertTrue(frame.evaluate("f").value().startsWith("function f()"));
+      } catch {
+        assertTrue(frame.sourceLineText().endsWith("throws"));
+      }
+    }
+  } catch(e) {
+    exception = e;
+    print(e, e.stack);
+  }
+};
+
+Debug.setListener(listener);
+
+(function f() {
+  f;
+  debugger;  // works
+})();
+
+(function f() {
+  () => f;
+  debugger;  // works
+})();
+
+(function f() {
+  debugger;  // throws
+})();
+
+assertNull(exception);
+
+Debug.setListener(null);

test/debugger/test-api.js

@@ -541,6 +541,9 @@ class DebugWrapper {
       case "boolean": {
         break;
       }
+      case "function": {
+        value = obj.description;
+      }
       default: {
         break;
       }