supersize: Track symbol aliases and shared symbols

tools/binary_size/libsupersize/testdata/mock_toolchain/mock_git.py

Index: tools/binary_size/libsupersize/testdata/mock_toolchain/mock_git.py
diff --git a/tools/binary_size/libsupersize/testdata/mock_toolchain/mock_git.py b/tools/binary_size/libsupersize/testdata/mock_toolchain/mock_git.py
new file mode 100644
index 0000000000000000000000000000000000000000..a1c1e0b461cf35e10496e18f5241670bf9882221
--- /dev/null
+++ b/tools/binary_size/libsupersize/testdata/mock_toolchain/mock_git.py
@@ -0,0 +1,14 @@
+# Copyright 2017 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.
+
+import sys
+
+
+def main():
+  assert sys.argv[-2:] == ['rev-parse', 'HEAD']
+  sys.stdout.write('abc123\n')
+
+
+if __name__ == '__main__':
+  main()