Teach users how to enable access to local files.

web/chromecom.js

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-/* globals chrome, PDFJS, PDFViewerApplication */
+/* globals chrome, PDFJS, PDFViewerApplication, OverlayManager */
 'use strict';
 
 var ChromeCom = (function ChromeComClosure() {
@@ -120,11 +120,89 @@ var ChromeCom = (function ChromeComClosure() {
               ' non-local page for security reasons.');
           return;
         }
+        isAllowedFileSchemeAccess(function(isAllowedAccess) {
+          if (isAllowedAccess) {
+            PDFViewerApplication.open(file, 0);
+          } else {
+            requestAccessToLocalFile(file);
+          }
+        });
+        return;
       }
       PDFViewerApplication.open(file, 0);
     });
   };
 
+  function isAllowedFileSchemeAccess(callback) {
+    ChromeCom.request('isAllowedFileSchemeAccess', null, callback);
+  }
+
+  function isRuntimeAvailable() {
+    try {
+      // When the extension is reloaded, the extension runtime is destroyed and
+      // the extension APIs become unavailable.
+      if (chrome.runtime && chrome.runtime.getManifest()) {
+        return true;
+      }
+    } catch (e) {}
+    return false;
+  }
+
+  function reloadIfRuntimeIsUnavailable() {
+    if (!isRuntimeAvailable()) {
+      location.reload();
+    }
+  }
+
+  var chromeFileAccessOverlayPromise;
+  function requestAccessToLocalFile(fileUrl) {
+    var onCloseOverlay = null;
+    if (top !== window) {
+      // When the extension reloads after receiving new permissions, the pages
+      // have to be reloaded to restore the extension runtime. Auto-reload
+      // frames, because users should not have to reload the whole page just to
+      // update the viewer.
+      // Top-level frames are closed by Chrome upon reload, so there is no need
+      // for detecting unload of the top-level frame. Should this ever change
+      // (crbug.com/511670), then the user can just reload the tab.
+      window.addEventListener('focus', reloadIfRuntimeIsUnavailable);
+      onCloseOverlay = function() {
+        window.removeEventListener('focus', reloadIfRuntimeIsUnavailable);
+        reloadIfRuntimeIsUnavailable();
+        OverlayManager.close('chromeFileAccessOverlay');
+      };
+    }
+    if (!chromeFileAccessOverlayPromise) {
+      chromeFileAccessOverlayPromise = OverlayManager.register(
+          'chromeFileAccessOverlay', onCloseOverlay, true);
+    }
+    chromeFileAccessOverlayPromise.then(function() {
+      var iconPath = chrome.runtime.getManifest().icons[48];
+      document.getElementById('chrome-pdfjs-logo-bg').style.backgroundImage =
+        'url(' + chrome.runtime.getURL(iconPath) + ')';
+
+      var link = document.getElementById('chrome-link-to-extensions-page');
+      link.href = 'chrome://extensions/?id=' + chrome.runtime.id;
+      link.onclick = function(e) {
+        // Direct navigation to chrome:// URLs is blocked by Chrome, so we
+        // have to ask the background page to open chrome://extensions/?id=...
+        e.preventDefault();
+        // Open in the current tab by default, because toggling the file access
+        // checkbox causes the extension to reload, and Chrome will close all
+        // tabs upon reload.
+        ChromeCom.request('openExtensionsPageForFileAccess', {
+          newTab: e.ctrlKey || e.metaKey || e.button === 1 || window !== top
+        });
+      };
+
+      // Show which file is being opened to help the user with understanding
+      // why this permission request is shown.
+      document.getElementById('chrome-url-of-local-file').textContent = fileUrl;
+
+      OverlayManager.open('chromeFileAccessOverlay');
+    });
+  }
+
   // This port is used for several purposes:
   // 1. When disconnected, the background page knows that the frame has unload.
   // 2. When the referrer was saved in history.state.chromecomState, it is sent

web/viewer-snippet-chrome-overlays.html

@@ -0,0 +1,24 @@
+<div id="chromeFileAccessOverlay" class="container hidden">
+  <div class="dialog">
+    <div class="row">
+      <!-- The extension icon (PDF.js logo) will be shown at the left, to help
+           users with recognizing which checkbox they have to click when they
+           visit chrome://extensions.
+      -->
+      <p id="chrome-pdfjs-logo-bg" style="
+          display: block;
+          padding-left: 60px;
+          min-height: 48px;
+          background-size: 48px;
+          background-repeat: no-repeat;
+          font-size: 14px;
+          line-height: 1.8em;
+          word-break: break-all;">
+        Click on "Allow access to file URLs" at
+        <a id="chrome-link-to-extensions-page">chrome://extensions</a>
+        <br>
+        to view <span id="chrome-url-of-local-file">this PDF file.</span>
+      </p>
+    </div>
+  </div>
+</div>

web/viewer.css

@@ -1371,6 +1371,10 @@ html[dir='rtl'] .attachmentsItem > button {
   vertical-align: middle;
 }
 
+.dialog :link {
+  color: white;
+}
+
 #passwordOverlay > .dialog {
   text-align: center;
 }

web/viewer.html

@@ -388,6 +388,9 @@ See https://github.com/adobe-type-tools/cmap-resources
             </div>
           </div>
         </div>
+<!--#if CHROME-->
+<!--#include viewer-snippet-chrome-overlays.html-->
+<!--#endif-->
       </div>  <!-- overlayContainer -->
 
     </div> <!-- outerContainer -->