[CRX] Add file chooser as fallback (fixes mozilla#9411)

Test case to exercise the different encodings:
1. Create a file "some file#@%M<br>%25 .pdf"
2. Build the extension with `gulp chromium` and load it in Chrome.
3. Go to `chrome://extensions/` and ensure that the
   "Allow access to file URLs" is disabled.
4. Try to open the file from step 1 in Chrome (maybe reload once).
5. PDF.js should be showing a file chooser button.
6. Click on that button and select a different file.

   Test: Check that a confirmation dialog pops up that warns about
   a different file name. Cancel the dialog.

7. Click on the button again and select the original file.

   Test: Check that the file opens as expected.

web/app.js

@@ -597,7 +597,7 @@ let PDFViewerApplication = {
           args = { length, };
         }
         if (originalURL !== undefined) {
-          file = { file: url, originalURL, };
+          file = { url, originalURL, };
         }
         PDFViewerApplication.open(file, args);
       },

web/chromecom.js

@@ -91,7 +91,7 @@ let ChromeCom = {
           if (isAllowedAccess) {
             callback(file);
           } else {
-            requestAccessToLocalFile(file, overlayManager);
+            requestAccessToLocalFile(file, overlayManager, callback);
           }
         });
       });
@@ -137,7 +137,7 @@ function reloadIfRuntimeIsUnavailable() {
 }
 
 let chromeFileAccessOverlayPromise;
-function requestAccessToLocalFile(fileUrl, overlayManager) {
+function requestAccessToLocalFile(fileUrl, overlayManager, callback) {
   let onCloseOverlay = null;
   if (top !== window) {
     // When the extension reloads after receiving new permissions, the pages
@@ -197,6 +197,29 @@ function requestAccessToLocalFile(fileUrl, overlayManager) {
     // why this permission request is shown.
     document.getElementById('chrome-url-of-local-file').textContent = fileUrl;
 
+    document.getElementById('chrome-file-fallback').onchange = function() {
+      let file = this.files[0];
+      if (file) {
+        let originalFilename = decodeURIComponent(fileUrl.split('/').pop());
+        let originalURL = fileUrl;
+        if (originalFilename !== file.name) {
+          let msg = 'The selected file does not match the original file.' +
+            '\nOriginal: ' + originalFilename +
+            '\nSelected: ' + file.name +
+            '\nDo you want to open the selected file?';
+          if (!confirm(msg)) {
+            this.value = '';
+            return;
+          }
+          // There is no way to retrieve the original URL from the File object.
+          // So just generate a fake path.
+          originalURL = 'file:///fakepath/to/' + encodeURIComponent(file.name);
+        }
+        callback(URL.createObjectURL(file), file.size, originalURL);
+        overlayManager.close('chromeFileAccessOverlay');
+      }
+    };
+
     overlayManager.open('chromeFileAccessOverlay');
   });
 }

web/viewer-snippet-chrome-overlays.html

@@ -22,5 +22,11 @@
         to view <span id="chrome-url-of-local-file">this PDF file.</span>
       </p>
     </div>
+    <div class="row">
+      <p>
+        or select the file again:
+        <input type="file" id="chrome-file-fallback" accept=".pdf">
+      </p>
+    </div>
   </div>
 </div>