Fixed #5791 -- Added early-bailout support for views (ETags and Last-modified).

This provides support for views that can have their ETag and/or Last-modified
values computed much more quickly than the view itself. Supports all HTTP
verbs (not just GET).

Documentation and tests need a little more fleshing out (I'm not happy with the
documentation at the moment, since it's a bit backwards), but the functionality
is correct.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10114 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/conditional_processing/views.py

@@ -0,0 +1,17 @@
+# -*- coding:utf-8 -*-
+from django.views.decorators.http import condition
+from django.http import HttpResponse
+
+from models import FULL_RESPONSE, LAST_MODIFIED, ETAG
+
+@condition(lambda r: ETAG, lambda r: LAST_MODIFIED)
+def index(request):
+    return HttpResponse(FULL_RESPONSE)
+
+@condition(last_modified_func=lambda r: LAST_MODIFIED)
+def last_modified(request):
+    return HttpResponse(FULL_RESPONSE)
+
+@condition(etag_func=lambda r: ETAG)
+def etag(request):
+    return HttpResponse(FULL_RESPONSE)