PDF viewer: Specify that the touchstart listener not be passive.

chrome/browser/resources/pdf/gesture_detector.js

 // Copyright 2016 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.
 
 'use strict';
 
 /**
  * A class that listens for touch events and produces events when these
  * touches form gestures (e.g. pinching).
  */
 class GestureDetector {
   /**
    * Constructs a GestureDetector.
    * @param {!Element} element The element to monitor for touch gestures.
    */
   constructor(element) {
     this.element_ = element;
 
-    this.element_.addEventListener('touchstart', this.onTouchStart_.bind(this));
-    this.element_.addEventListener('touchmove', this.onTouch_.bind(this));
-    this.element_.addEventListener('touchend', this.onTouch_.bind(this));
-    this.element_.addEventListener('touchcancel', this.onTouch_.bind(this));
+    this.element_.addEventListener(
+        'touchstart', this.onTouchStart_.bind(this), { passive: false });
+    this.element_.addEventListener(
+        'touchmove', this.onTouch_.bind(this), { passive: true });
+    this.element_.addEventListener(
+        'touchend', this.onTouch_.bind(this), { passive: true });
+    this.element_.addEventListener(
+        'touchcancel', this.onTouch_.bind(this), { passive: true });
 
     this.pinchStartEvent_ = null;
     this.lastEvent_ = null;
 
     this.listeners_ = new Map([
       ['pinchstart', []],
       ['pinchupdate', []],
       ['pinchend', []]
     ]);
   }
@@ skipping 118 matching lines @@
    */
   static center_(event) {
     let touch1 = event.touches[0];
     let touch2 = event.touches[1];
     return {
       x: (touch1.clientX + touch2.clientX) / 2,
       y: (touch1.clientY + touch2.clientY) / 2
     };
   }
 };