Fix images and HttpStreamFactoryImpl references in docs.

It's HttpStreamFactory now, and HttpStreamFactoryImpl::Request and
HttpStreamFactory have been folded together.

Also Gerrit does not support SVGs, only PNGs. Fix the images.
Unfortunately, PNG or SVG, the diagram is very small and barely readable.
But at least it shows up now.

Change-Id: Ie8bbc519cd120bf151edd98b588dfddb91f0df21
Reviewed-on: https://chromium-review.googlesource.com/c/1396668
Reviewed-by: Matt Menke <[email protected]>
Commit-Queue: David Benjamin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#621177}
diff --git a/net/docs/generate-dot-to-png.py b/net/docs/generate-dot-to-png.py
new file mode 100755
index 0000000..15447eb
--- /dev/null
+++ b/net/docs/generate-dot-to-png.py
@@ -0,0 +1,24 @@
+#!/usr/bin/python
+# Copyright 2018 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""The diagrams included in the network stack documentation were
+generated with Graphviz, and both source (.dot) and output (.svg) are
+included in the repository.  If graphviz is installed, the output may
+be regenerated by running this script."""
+
+import glob
+import os
+import subprocess
+
+def main():
+  for dot_filename in glob.glob("*.dot"):
+    png_filename = os.path.splitext(dot_filename)[0] + ".png"
+    print "Generating %s from %s" % (png_filename, dot_filename)
+    subprocess.check_call(["dot", "-Tpng", dot_filename, "-o", png_filename])
+    subprocess.check_call(["optipng", png_filename])
+
+
+if __name__ == "__main__":
+  main()