Make check_gn_headers.py run on Windows

build/check_gn_headers_unittest.py

Index: build/check_gn_headers_unittest.py
diff --git a/build/check_gn_headers_unittest.py b/build/check_gn_headers_unittest.py
index e0853fdefef0c1129387ed96ae625977dcb2cf2e..20b41f4b957eb9a83f1850d79d7c0495637585aa 100755
--- a/build/check_gn_headers_unittest.py
+++ b/build/check_gn_headers_unittest.py
@@ -29,7 +29,6 @@ obj/c.o: #deps 1, deps mtime 123 (VALID)
     ../../dir3/path/b.h
     ../../c3.hh
 '''
-ninja_input_win = ninja_input.replace('/', '\\')
 
 
 gn_input = json.loads(r'''
@@ -75,22 +74,6 @@ class CheckGnHeadersTest(unittest.TestCase):
     ])
     self.assertEquals(headers, expected)
 
-  def testNinjaWin(self):
-    old_sep = os.sep
-    os.sep = '\\'
-
-    headers = check_gn_headers.ParseNinjaDepsOutput(
-        ninja_input_win.split('\n'), 'out\\Release')
-    expected = set([
-        'dir\\path\\b.h',
-        'c.hh',
-        'dir3\\path\\b.h',
-        'c3.hh',
-    ])
-    self.assertEquals(headers, expected)
-
-    os.sep = old_sep
-
   def testGn(self):
     headers = check_gn_headers.ParseGNProjectJSON(gn_input,
                                                   'out/Release', 'tmp')