Add shortcuts for zoom, print and saving PDFs.

chrome/browser/resources/pdf/pdf.js

Index: chrome/browser/resources/pdf/pdf.js
diff --git a/chrome/browser/resources/pdf/pdf.js b/chrome/browser/resources/pdf/pdf.js
index 6cc8421484a0f248ca01fd40d30fedeb6ef68a68..ca9e63b1700a5e12b2edffa563a9e28cf6982247 100644
--- a/chrome/browser/resources/pdf/pdf.js
+++ b/chrome/browser/resources/pdf/pdf.js
@@ -131,7 +131,6 @@ function load() {
   $('save-button-link').href = streamDetails.originalURL;
   $('print-button').addEventListener('click', print);
 
-
   // Setup keyboard event listeners.
   document.onkeydown = function(e) {
     switch (e.keyCode) {
@@ -164,6 +163,29 @@ function load() {
           e.preventDefault();
         }
         return;
+      case 187:  // +/= key.
+      case 107:  // Numpad + key.
+        if (e.ctrlKey)
+          viewport.zoomIn();
+        return;
+      case 189:  // -/_ key.
+      case 109:  // Numpad - key.
+        if (e.ctrlKey)
+          viewport.zoomOut();
+        return;
+      case 83:  // s key.
+        if (e.ctrlKey) {
+          // Simulate a click on the button so that the <a download ...>
+          // attribute is used.
+          $('save-button-link').click();
+        }
+        return;
+      case 80:  // p key.
+        if (e.ctrlKey) {
+          print();
+          e.preventDefault();
+        }
+        return;
     }
   };
 }