debug: LoadLookupSlot should initialize receiver for modules..

.. otherwise V8 crashes on attempt to use imported function as part
of expression passed to Debugger.evaluateOnCallFrame.

R=neis@chromium.org

Bug: chromium:878029
Cq-Include-Trybots: luci.chromium.try:linux_chromium_headless_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I61b837f5c7b84a80d91a9cdaaac0422a24aa1620
Reviewed-on: https://chromium-review.googlesource.com/1241475Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56216}

src/runtime/runtime-scopes.cc

@@ -801,6 +801,8 @@ MaybeHandle<Object> LoadLookupSlot(Isolate* isolate, Handle<String> name,
   if (isolate->has_pending_exception()) return MaybeHandle<Object>();
 
   if (!holder.is_null() && holder->IsModule()) {
+    Handle<Object> receiver = isolate->factory()->undefined_value();
+    if (receiver_return) *receiver_return = receiver;
     return Module::LoadVariable(isolate, Handle<Module>::cast(holder), index);
   }
   if (index != Context::kNotFound) {

test/inspector/debugger/evaluate-at-first-module-line-expected.txt

+Evaluate at first line of module should not crash
+{
+    id : <messageId>
+    result : {
+        result : {
+            description : 0
+            type : number
+            value : 0
+        }
+    }
+}

test/inspector/debugger/evaluate-at-first-module-line.js

+// Copyright 2018 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.
+
+const {session, contextGroup, Protocol} =
+  InspectorTest.start('Evaluate at first line of module should not crash');
+
+const utilsModule = `export function identity(value) {
+  return value;
+}`;
+
+const mainModule = `import {identity} from 'utils';
+console.log(identity(0));`;
+
+(async function test() {
+  Protocol.Debugger.enable();
+  Protocol.Debugger.setBreakpointByUrl({
+    lineNumber: 1,
+    url: 'main'
+  });
+
+  contextGroup.addModule(utilsModule, 'utils');
+  contextGroup.addModule(mainModule, 'main');
+  const { params: { callFrames } } = await Protocol.Debugger.oncePaused();
+  const result = await Protocol.Debugger.evaluateOnCallFrame({
+    callFrameId: callFrames[0].callFrameId,
+    expression: 'identity(0)'
+  });
+  InspectorTest.logMessage(result);
+  InspectorTest.completeTest();
+})()