Use the chrome.devtools.inspectedWindow API to interact with the inspected window: obtain the tab ID for the inspected page, evaluate the code in the context of the inspected window, reload the page, or obtain the list of resources within the page.

class ChromeDevtoolsInspectedWindow extends ChromeApi {
 static final JsObject _devtools_inspectedWindow = chrome['devtools']['inspectedWindow'];

 ChromeDevtoolsInspectedWindow._();

 bool get available => _devtools_inspectedWindow != null;

 /**
  * The ID of the tab being inspected. This ID may be used with chrome.tabs.*
  * API.
  */
 int get tabId => _devtools_inspectedWindow['tabId'];

 /**
  * Evaluates a JavaScript expression in the context of the main frame of the
  * inspected page. The expression must evaluate to a JSON-compliant object,
  * otherwise an exception is thrown.
  * 
  * [expression] An expression to evaluate.
  * 
  * Returns:
  * [result] The result of evaluation.
  * [isException] Set if an exception was caught while evaluating the
  * expression.
  */
 Future<EvalResult> eval(String expression) {
   if (_devtools_inspectedWindow == null) _throwNotAvailable();

   var completer = new ChromeCompleter<EvalResult>.twoArgs(EvalResult._create);
   _devtools_inspectedWindow.callMethod('eval', [expression, completer.callback]);
   return completer.future;
 }

 /**
  * Reloads the inspected page.
  */
 void reload([DevtoolsInspectedWindowReloadParams reloadOptions]) {
   if (_devtools_inspectedWindow == null) _throwNotAvailable();

   _devtools_inspectedWindow.callMethod('reload', [jsify(reloadOptions)]);
 }

 /**
  * Retrieves the list of resources from the inspected page.
  * 
  * Returns:
  * The resources within the page.
  */
 Future<List<Resource>> getResources() {
   if (_devtools_inspectedWindow == null) _throwNotAvailable();

   var completer = new ChromeCompleter<List<Resource>>.oneArg((e) => listify(e, _createResource));
   _devtools_inspectedWindow.callMethod('getResources', [completer.callback]);
   return completer.future;
 }

 /**
  * Fired when a new resource is added to the inspected page.
  */
 Stream<Resource> get onResourceAdded => _onResourceAdded.stream;

 final ChromeStreamController<Resource> _onResourceAdded =
     new ChromeStreamController<Resource>.oneArg(_devtools_inspectedWindow, 'onResourceAdded', _createResource);

 /**
  * Fired when a new revision of the resource is committed (e.g. user saves an
  * edited version of the resource in the Developer Tools).
  */
 Stream<OnResourceContentCommittedEvent> get onResourceContentCommitted => _onResourceContentCommitted.stream;

 final ChromeStreamController<OnResourceContentCommittedEvent> _onResourceContentCommitted =
     new ChromeStreamController<OnResourceContentCommittedEvent>.twoArgs(_devtools_inspectedWindow, 'onResourceContentCommitted', _createOnResourceContentCommittedEvent);

 void _throwNotAvailable() {
   throw new UnsupportedError("'chrome.devtools.inspectedWindow' is not available");
 }
}