[debugger] correctly find inner function scope.

Nested arrow functions can have the same end positions, so
the end position is unsuitable to decide whether a scope is
an inner function scope.

BUG=chromium:696202
R=jgruber@chromium.org, kozyatinskiy@chromium.org

Review-Url: https://codereview.chromium.org/2751573003
Cr-Commit-Position: refs/heads/master@{#43797}

src/debug/debug-scopes.cc

@@ -838,8 +838,12 @@ void ScopeIterator::GetNestedScopeChain(Isolate* isolate, Scope* scope,
                                         int position) {
   if (scope->is_function_scope()) {
     // Do not collect scopes of nested inner functions inside the current one.
+    // Nested arrow functions could have the same end positions.
     Handle<JSFunction> function = frame_inspector_->GetFunction();
-    if (scope->end_position() < function->shared()->end_position()) return;
+    if (scope->start_position() > function->shared()->start_position() &&
+        scope->end_position() <= function->shared()->end_position()) {
+      return;
+    }
   }
   if (scope->is_hidden()) {
     // We need to add this chain element in case the scope has a context

test/inspector/debugger/step-into-nested-arrow-expected.txt

+Checks that stepInto nested arrow function doesn't produce crash.
+paused
+(anonymous) (test.js:2:0)
+(anonymous) (:0:6)
+paused
+rec (test.js:1:19)
+(anonymous) (test.js:2:0)
+(anonymous) (:0:6)
+paused
+rec (test.js:2:5)
+(anonymous) (test.js:2:0)
+(anonymous) (:0:6)
+paused
+(anonymous) (test.js:2:5)
+(anonymous) (:0:6)
+paused
+(anonymous) (:0:8)

test/inspector/debugger/step-into-nested-arrow.js

+// Copyright 2017 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.
+
+InspectorTest.log(
+    'Checks that stepInto nested arrow function doesn\'t produce crash.');
+
+InspectorTest.setupScriptMap();
+InspectorTest.addScript(`
+const rec = (x) => (y) =>
+rec();
+//# sourceURL=test.js`);
+
+Protocol.Debugger.onPaused(message => {
+  InspectorTest.log("paused");
+  InspectorTest.logCallFrames(message.params.callFrames);
+  Protocol.Debugger.stepInto();
+})
+
+Protocol.Debugger.enable();
+Protocol.Debugger.setBreakpointByUrl({ url: 'test.js', lineNumber: 2 })
+  .then(() => Protocol.Runtime.evaluate({ expression: 'rec(5)(4)' }))
+  .then(InspectorTest.completeTest);

test/inspector/protocol-test.js

@@ -160,6 +160,7 @@ InspectorTest.logSourceLocation = function(location)
     var line = lines[location.lineNumber];
     line = line.slice(0, location.columnNumber) + '#' + (line.slice(location.columnNumber) || '');
     lines[location.lineNumber] = line;
+    lines = lines.filter(line => line.indexOf('//# sourceURL=') === -1);
     InspectorTest.log(lines.slice(Math.max(location.lineNumber - 1, 0), location.lineNumber + 2).join('\n'));
     InspectorTest.log('');
   }