Fix button event on mouse events.

third_party/WebKit/LayoutTests/external/wpt_automation/pointerevents/pointerevent_common_input.js

 // This file contains the commonly used functions in pointerevent tests.
 
 const scrollOffset = 20;
 const boundaryOffset = 2;
 
 function delayPromise(delay) {
   return new Promise(function(resolve, reject) {
     window.setTimeout(resolve, delay);
   });
 }
@@ skipping 112 matching lines @@
               {name: 'pointerUp'}
             ]
           }],
           resolve);
     } else {
       reject();
     }
   });
 }
 
-function mouseDragInTargets(targetSelectorList) {
+function mouseDragInTargets(targetSelectorList, button) {
   return new Promise(function(resolve, reject) {
     if (window.chrome && chrome.gpuBenchmarking) {
+      if (button === undefined) {
+        button = 'left';
+      }
       scrollPageIfNeeded(targetSelectorList[0], document);
       var target = document.querySelector(targetSelectorList[0]);
       var targetRect = target.getBoundingClientRect();
       var xPosition = targetRect.left + boundaryOffset;
       var yPosition = targetRect.top + boundaryOffset;
       var pointerActions = [{'source': 'mouse'}];
       var pointerAction = pointerActions[0];
       pointerAction.actions = [];
       pointerAction.actions.push(
-          {name: 'pointerDown', x: xPosition, y: yPosition});
+          {name: 'pointerDown', x: xPosition, y: yPosition, button: button});
       for (var i = 1; i < targetSelectorList.length; i++) {
         scrollPageIfNeeded(targetSelectorList[i], document);
         target = document.querySelector(targetSelectorList[i]);
         targetRect = target.getBoundingClientRect();
         xPosition = targetRect.left + boundaryOffset;
         yPosition = targetRect.top + boundaryOffset;
         pointerAction.actions.push(
-            {name: 'pointerMove', x: xPosition, y: yPosition});
+            {name: 'pointerMove', x: xPosition, y: yPosition, button: button});
       }
-      pointerAction.actions.push({name: 'pointerUp'});
+      pointerAction.actions.push({name: 'pointerUp', button: button});
       chrome.gpuBenchmarking.pointerActionSequence(pointerActions, resolve);
     } else {
       reject();
     }
   });
 }
 
 function mouseDragInTarget(targetSelector) {
   return mouseDragInTargets([targetSelector, targetSelector]);
 }
@@ skipping 309 matching lines @@
   });
 }
 
 {
   var pointerevent_automation = async_test("PointerEvent Automation");
   // Defined in every test and should return a promise that gets resolved when input is finished.
   inject_input().then(function() {
     pointerevent_automation.done();
   });
 }