Change image/jpg Content-Type to image/jpeg.

This makes QtWebKit display images with a (nonstandard) image/jpg content-type,
e.g. http://m.c.lnkd.licdn.com/mpr/mpr/p/2/005/07b/08a/018245a.jpg (instead of
downloading them).

qutebrowser/network/networkmanager.py

@@ -19,6 +19,8 @@
 
 """Our own QNetworkAccessManager."""
 
+from functools import partial
+
 from PyQt5.QtCore import pyqtSlot, PYQT_VERSION, QCoreApplication
 from PyQt5.QtNetwork import QNetworkAccessManager, QNetworkReply
 
@@ -35,6 +37,7 @@ import qutebrowser.utils.log as log
 from qutebrowser.network.qutescheme import QuteSchemeHandler
 from qutebrowser.network.schemehandler import ErrorNetworkReply
 from qutebrowser.utils.usertypes import PromptMode
+from qutebrowser.utils.http import change_content_type
 
 
 class NetworkManager(QNetworkAccessManager):
@@ -137,7 +140,6 @@ class NetworkManager(QNetworkAccessManager):
         elif scheme in self._scheme_handlers:
             return self._scheme_handlers[scheme].createRequest(
                 op, req, outgoing_data)
-        else:
         if config.get('network', 'do-not-track'):
             dnt = '1'.encode('ascii')
         else:
@@ -160,4 +162,10 @@ class NetworkManager(QNetworkAccessManager):
             reply = super().createRequest(op, req, outgoing_data)
         self._requests.append(reply)
         reply.destroyed.connect(lambda obj: self._requests.remove(obj))
+        # Some servers (e.g. the LinkedIn CDN) send a non-standard image/jpg
+        # header for jpg images. We change this to image/jpeg (defined in RFC
+        # 1341 section 7.5: https://tools.ietf.org/html/rfc1341) so QtWebKit
+        # displays this instead of downloading it.
+        reply.metaDataChanged.connect(partial(change_content_type, reply,
+                                              {'image/jpg': 'image/jpeg'}))
         return reply

qutebrowser/utils/http.py

@@ -103,7 +103,7 @@ def change_content_type(reply, mapping):
     try:
         content_type = mapping[content_type]
     except KeyError:
-        pass
+        return
     if rest is not None:
         header = ';'.join((content_type, rest))
     else: