diff -r 000000000000 -r 6474c204b198 layout/generic/frame-graph.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/generic/frame-graph.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,41 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Take the *.framedata files from graph-frameclasses.js and combine them
+into a single graphviz file.
+
+stdin: a list of .framedata file names (e.g. from xargs)
+stdout: a graphviz file
+
+e.g. `find <objdir> -name "*.framedata" | python aggregate-frameclasses.py |
+  dot -Tpng -o frameclasses-graph.png -`
+"""
+
+import sys
+
+classdict = {}
+
+for line in sys.stdin:
+    file = line.strip()
+    fd = open(file)
+
+    output = None
+    for line in fd:
+        if line.startswith('CLASS-DEF: '):
+            cname = line[11:-1]
+            if cname not in classdict:
+                output = classdict[cname] = []
+            else:
+                output = None
+        elif output is not None:
+            output.append(line)
+
+sys.stdout.write('digraph g {\n')
+
+for olist in classdict.itervalues():
+    for line in olist:
+        sys.stdout.write(line)
+
+sys.stdout.write('}\n')