Integration test for updatable system font.

This test:
(1) signs a font file with the test key.
(2) side-loads the test cert to the device under test.
(3) verifies that the signed font file can be installed.

The device must be rootable for doing step (2).

Bug: 176939176
Test: atest UpdatableSystemFontTest
Change-Id: I7a9b614aa3c77589c3495b663cb76056ba657006

tools/fonts/update_font_metadata.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python
+
+import argparse
+
+from fontTools import ttLib
+
+
+def update_font_revision(font, revisionSpec):
+    if revisionSpec.startswith('+'):
+      font['head'].fontRevision += float(revisionSpec[1:])
+    else:
+      font['head'].fontRevision = float(revisionSpec)
+
+
+def main():
+    args_parser = argparse.ArgumentParser(description='Update font file metadata')
+    args_parser.add_argument('--input', help='Input otf/ttf font file.')
+    args_parser.add_argument('--output', help='Output file for updated font file.')
+    args_parser.add_argument('--revision', help='Updated font revision. Use + to update revision based on the current revision')
+    args = args_parser.parse_args()
+
+    font = ttLib.TTFont(args.input)
+    update_font_revision(font, args.revision)
+    font.save(args.output)
+
+if __name__ == "__main__":
+    main()