Improve symbol_extractor.CreateNameToSymbolInfo handling of duplicate symbols.

tools/cygprofile/symbol_extractor_unittest.py

 #!/usr/bin/python
 # Copyright 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.
 
 import symbol_extractor
 import unittest
 
 class TestSymbolInfo(unittest.TestCase):
   def testIgnoresBlankLine(self):
@@ skipping 85 matching lines @@
 
   def testCreateNameToSymbolInfo(self):
     name_to_symbol_info = symbol_extractor.CreateNameToSymbolInfo(
         self.symbol_infos)
     self.assertEquals(len(name_to_symbol_info), 3)
     for i in range(3):
       name = self.symbol_infos[i].name
       self.assertIn(name, name_to_symbol_info)
       self.assertEquals(self.symbol_infos[i], name_to_symbol_info[name])
 
+  def testSymbolCollisions(self):
+    symbol_infos_with_collision = list(self.symbol_infos)
+    symbol_infos_with_collision.append(symbol_extractor.SymbolInfo(
+        'secondNameAtOffset', 0x84, 42, '.text'))
+
+    # The symbol added above should not affect the output.
+    name_to_symbol_info = symbol_extractor.CreateNameToSymbolInfo(
+        self.symbol_infos)
+    self.assertEquals(len(name_to_symbol_info), 3)
+    for i in range(3):
+      name = self.symbol_infos[i].name
+      self.assertIn(name, name_to_symbol_info)
+      self.assertEquals(self.symbol_infos[i], name_to_symbol_info[name])
 
 if __name__ == '__main__':
   unittest.main()