[devtools] Support different encodings for Page.CaptureScreenshot.

third_party/WebKit/Source/devtools/front_end/emulation/DeviceModeView.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 /**
  * @unrestricted
  */
 Emulation.DeviceModeView = class extends UI.VBox {
   constructor() {
     super(true);
     this.setMinimumSize(150, 150);
@@ skipping 358 matching lines @@
     var rect = this._contentArea.getBoundingClientRect();
     var availableSize = new UI.Size(Math.max(rect.width * zoomFactor, 1), Math.max(rect.height * zoomFactor, 1));
     var outlineVisible = this._model.deviceOutlineSetting().get();
 
     if (availableSize.width < this._model.screenRect().width ||
         availableSize.height < this._model.screenRect().height) {
       UI.inspectorView.minimize();
       this._model.deviceOutlineSetting().set(false);
     }
 
-    mainTarget.pageAgent().captureScreenshot(screenshotCaptured.bind(this));
+    mainTarget.pageAgent().captureScreenshot('png', 100, screenshotCaptured.bind(this));
 
     /**
      * @param {?Protocol.Error} error
      * @param {string} content
      * @this {Emulation.DeviceModeView}
      */
     function screenshotCaptured(error, content) {
       this._model.deviceOutlineSetting().set(outlineVisible);
       var dpr = window.devicePixelRatio;
       var outlineRect = this._model.outlineRect().scale(dpr);
@@ skipping 175 matching lines @@
     return Promise.resolve();
   }
 
   /**
    * @param {number} size
    */
   _onMarkerClick(size) {
     this._applyCallback.call(null, size);
   }
 };