Implement sendKeyEvent print preview function for OOP PDF.

chrome/browser/resources/pdf/pdf_scripting_api.js

Index: chrome/browser/resources/pdf/pdf_scripting_api.js
diff --git a/chrome/browser/resources/pdf/pdf_scripting_api.js b/chrome/browser/resources/pdf/pdf_scripting_api.js
index 81774f36a3ea07638ed1671f4f76507b08a2b7db..2b98c7c797323f0ed02f790c0f0f4ce50812651d 100644
--- a/chrome/browser/resources/pdf/pdf_scripting_api.js
+++ b/chrome/browser/resources/pdf/pdf_scripting_api.js
@@ -149,8 +149,10 @@ PDFScriptingAPI.prototype = {
    * @param {number} keyCode the key code to send to the extension.
    */
   sendKeyEvent: function(keyCode) {
-    // TODO(raymes): Figure out a way to do this. It's only used to do scrolling
-    // the viewport, so probably just expose viewport controls instead.
+    this.sendMessage_({
+      type: 'sendKeyEvent',
+      keyCode: keyCode
+    });
   },
 };