scanning: Use arrow functions to call into callbacks

Using arrow functions is recommended over binding since arrow functions
permit explicitly specifying which parameters to pass to the callbacks.

Bug: 1059779
Change-Id: I25279d8e39f6635a41719e794620c76ee956545f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2457406Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Commit-Queue: Jesse Schettler <jschettler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814963}

chromeos/components/scanning/resources/scanning_app.js

@@ -85,7 +85,10 @@ Polymer({
 
   /** @override */
   ready() {
-    this.scanService_.getScanners().then(this.onScannersReceived_.bind(this));
+    this.scanService_.getScanners().then(
+        /*@type {!{scanners: !ScannerArr}}*/ (response) => {
+          this.onScannersReceived_(response);
+        });
   },
 
   /**
@@ -137,7 +140,12 @@ Polymer({
 
     this.scanService_
         .getScannerCapabilities(this.scannerIds_.get(selectedScannerId))
-        .then(this.onCapabilitiesReceived_.bind(this));
+        .then(
+            /*@type {!{capabilities:
+                   !chromeos.scanning.mojom.ScannerCapabilities}}*/
+            (response) => {
+              this.onCapabilitiesReceived_(response);
+            });
   },
 
   /** @private */
@@ -163,7 +171,8 @@ Polymer({
         .scan(this.scannerIds_.get(this.selectedScannerId), settings)
         .then(
             /*@type {!{success: boolean}}*/ (response) => {
-                this.onScanCompleted_(response)});
+              this.onScanCompleted_(response);
+            });
   },
 
   /**