Add qute://pdfjs/file to get files

Cross-origin requests aren't supported for qute:// URLs, and qute:// can't
access file://, so we need to get the files that way.

qutebrowser/browser/pdfjs.py

@@ -155,7 +155,13 @@ def should_use_pdfjs(mimetype):
 def get_main_url(filename):
     """Get the URL to be opened to view a local PDF."""
     url = QUrl('qute://pdfjs/web/viewer.html')
+
+    file_url = QUrl('qute://pdfjs/file')
+    file_url_query = QUrlQuery()
+    file_url_query.addQueryItem('filename', filename)
+    file_url.setQuery(file_url_query)
+
     query = QUrlQuery()
-    query.addQueryItem('file', QUrl.fromLocalFile(filename).toString())
+    query.addQueryItem('file', file_url.toString())
     url.setQuery(query)
     return url

qutebrowser/browser/qutescheme.py

@@ -523,6 +523,16 @@ def qute_pastebin_version(_url):
 @add_handler('pdfjs')
 def qute_pdfjs(url):
     """Handler for qute://pdfjs. Return the pdf.js viewer."""
+    # FIXME be more strict about allowed files here
+    if url.path() == '/file':
+        filename = QUrlQuery(url).queryItemValue('filename')
+        with open(filename, 'rb') as f:
+            data = f.read()
+        mimetype, _encoding = mimetypes.guess_type(filename)
+        if mimetype is None:
+            mimetype = 'application/octet-stream'
+        return mimetype, data
+
     try:
         data = pdfjs.get_pdfjs_res(url.path())
     except pdfjs.PDFJSNotFound as e: