Add scripts to generate simple test data for certificate verification.

net/data/verify_certificate_chain_unittest/generate-intermediary-lacks-signing-key-usage.py

Index: net/data/verify_certificate_chain_unittest/generate-intermediary-lacks-signing-key-usage.py
diff --git a/net/data/verify_certificate_chain_unittest/generate-intermediary-lacks-signing-key-usage.py b/net/data/verify_certificate_chain_unittest/generate-intermediary-lacks-signing-key-usage.py
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+++ b/net/data/verify_certificate_chain_unittest/generate-intermediary-lacks-signing-key-usage.py
@@ -0,0 +1,28 @@
+#!/usr/bin/python
+# Copyright (c) 2015 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.
+
+"""Certificate chain with 1 intermediary and a trusted root. The intermediary
+contains a keyUsage extension, HOWEVER it does not contain the keyCertSign bit.
+Hence validation is expected to fail."""
+
+import common
+
+# Self-signed root certificate (part of trust store).
+root = common.CreateSelfSignedRootCertificate('Root')
+
+# Intermediary that is missing keyCertSign.
+intermediary = common.CreateIntermediaryCertificate('Intermediary', root)
+intermediary.GetExtensions().SetProperty('keyUsage',
+    'critical,digitalSignature,keyEncipherment')
+
+# Target certificate.
+target = common.CreateEndEntityCertificate('Target', intermediary)
+
+chain = [target, intermediary]
+trusted = [root]
+time = common.DEFAULT_TIME
+verify_result = False
+
+common.WriteTestFile(__doc__, chain, trusted, time, verify_result)