Handle the keyboard event for ctrl+a inside pdf.js instead of out_of_process_pdf.cc

chrome/browser/resources/pdf/pdf.js

 // Copyright 2013 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';
 
 /**
  * @return {number} Width of a scrollbar in pixels
  */
 function getScrollbarWidth() {
@@ skipping 200 matching lines @@
           position.x += Viewport.SCROLL_INCREMENT;
           this.viewport.position = position;
         }
         return;
       case 40:  // Down arrow key.
         if (fromScriptingAPI) {
           position.y += Viewport.SCROLL_INCREMENT;
           this.viewport.position = position;
         }
         return;
+      case 65:  // a key.
+        if (e.ctrlKey || e.metaKey) {
+          this.plugin_.postMessage({
+            type: 'selectAll',
+          });
+        }
+        return;
       case 83:  // s key.
         if (e.ctrlKey || e.metaKey) {
           // Simulate a click on the button so that the <a download ...>
           // attribute is used.
           $('save-button-link').click();
           // Since we do the saving of the page.
           e.preventDefault();
         }
         return;
       case 80:  // p key.
@@ skipping 325 matching lines @@
     window.parent.postMessage(message, '*');
   },
 
   /**
    * @type {Viewport} the viewport of the PDF viewer.
    */
   get viewport() {
     return this.viewport_;
   }
 };