[inspector] added flag for injected-script-source debugging

test/inspector/debugger/stepping-with-exposed-injected-script.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.
+// Flags: --expose-inspector-scripts
+
+Protocol.Debugger.onPaused(message => {
+  let url = InspectorTest._scriptMap.get(message.params.callFrames[0].location.scriptId).url;
+  if (url !== 'test.js') {
+    InspectorTest.log('InjectedSciptSource on stack.');
+    InspectorTest.completeTest();
+  }
+  Protocol.Debugger.stepInto();
+});
+
+InspectorTest.setupScriptMap();
+Protocol.Debugger.enable();
+Protocol.Debugger.pause();
+Protocol.Runtime.evaluate({expression: 'console.log(42)//# sourceURL=test.js'})
+  .then(() => InspectorTest.log('InjectedSciptSource was not reached'))
+  .then(InspectorTest.completeTest);