Fix infinite recursion in find_depot_tools

tools/find_depot_tools.py

Index: tools/find_depot_tools.py
diff --git a/tools/find_depot_tools.py b/tools/find_depot_tools.py
index 4647738d55977efdb4ca15d30d908c07be20c3c2..0fa151b162c8da3f599ff461024f9cc3e46212a2 100644
--- a/tools/find_depot_tools.py
+++ b/tools/find_depot_tools.py
@@ -23,11 +23,13 @@ def add_depot_tools_to_path():
       return i
   # Rare case, it's not even in PATH, look upward up to root.
   root_dir = os.path.dirname(os.path.abspath(__file__))
-  while root_dir:
+  previous_dir = os.path.abspath(__file__)
+  while root_dir and root_dir != previous_dir:
     if os.path.isfile(os.path.join(root_dir, 'depot_tools', 'breakpad.py')):
       i = os.path.join(root_dir, 'depot_tools')
       sys.path.append(i)
       return i
+    previous_dir = root_dir
     root_dir = os.path.dirname(root_dir)
   print >> sys.stderr, 'Failed to find depot_tools'
   return None