cros_generate_breakpad_symbols: use cros_build_lib.Open helper

No need to duplicate the logic here.

BUG=None
TEST=`./buildbot/run_tests` passes

Change-Id: Ic11d27a02da573872f64a8e452ace0b6d9c08289
Reviewed-on: https://chromium-review.googlesource.com/185583
Reviewed-by: Yu-Ju Hong <yjhong@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros_generate_breakpad_symbols.py b/scripts/cros_generate_breakpad_symbols.py
index 280fc32..370e7c0 100644
--- a/scripts/cros_generate_breakpad_symbols.py
+++ b/scripts/cros_generate_breakpad_symbols.py
@@ -50,15 +50,12 @@
   Raises:
     ValueError if the first line of |sym_file| is invalid
   """
-  read_it = lambda x: x.readline().split()
-  if isinstance(sym_file, basestring):
-    with open(sym_file, 'r') as f:
-      header = read_it(f)
-  else:
-    header = read_it(sym_file)
+  with cros_build_lib.Open(sym_file) as f:
+    header = f.readline().split()
 
   if header[0] != 'MODULE' or len(header) != 5:
     raise ValueError('header of sym file is invalid')
+
   return SymbolHeader(os=header[1], cpu=header[2], id=header[3], name=header[4])