chore(types): make TS think that ElementArrayFinder and ElementFinder…

… are compatible with WebElement (#3732)

lib/element.ts

@@ -17,29 +17,8 @@ let WEB_ELEMENT_FUNCTIONS = [
   'getInnerHtml', 'getId', 'getRawId', 'serialize', 'takeScreenshot'
 ];
 
-// Explicitly define webdriver.WebElement.
-// TODO: extend WebElement from selenium-webdriver typings
-export class WebdriverWebElement {
-  getDriver: () => WebDriver;
-  getId: () => wdpromise.Promise<any>;
-  getRawId: () => wdpromise.Promise<string>;
-  serialize: () => wdpromise.Promise<any>;
-  findElement: (subLocator: Locator) => wdpromise.Promise<any>;
-  click: () => wdpromise.Promise<void>;
-  sendKeys: (...args: (string|wdpromise.Promise<string>)[]) => wdpromise.Promise<void>;
-  getTagName: () => wdpromise.Promise<string>;
-  getCssValue: (cssStyleProperty: string) => wdpromise.Promise<string>;
-  getAttribute: (attributeName: string) => wdpromise.Promise<string>;
-  getText: () => wdpromise.Promise<string>;
-  getSize: () => wdpromise.Promise<ISize>;
-  getLocation: () => wdpromise.Promise<ILocation>;
-  isEnabled: () => wdpromise.Promise<boolean>;
-  isSelected: () => wdpromise.Promise<boolean>;
-  submit: () => wdpromise.Promise<void>;
-  clear: () => wdpromise.Promise<void>;
-  isDisplayed: () => wdpromise.Promise<boolean>;
-  takeScreenshot: (opt_scroll?: boolean) => wdpromise.Promise<string>;
-}
+export class WebdriverWebElement {}
+export interface WebdriverWebElement extends WebElement {}
 
 /**
  * ElementArrayFinder is used for operations on an array of elements (as opposed