Fix typo from r288440

BUG=
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/452313003

Cr-Commit-Position: refs/heads/master@{#288447}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288447 0039d316-1c4b-4281-b951-d872f2087c98

PRESUBMIT.py

@@ -921,7 +921,7 @@ def _CheckSpamLogging(input_api, output_api):
                      r"startup_browser_creator\.cc$",
                  r"^chrome[\\\/]installer[\\\/]setup[\\\/].*",
                  r"chrome[\\\/]browser[\\\/]diagnostics[\\\/]" +
-                     r"diagnostics_writer.cc"
+                     r"diagnostics_writer\.cc$",
                  r"^chrome_elf[\\\/]dll_hash[\\\/]dll_hash_main\.cc$",
                  r"^chromecast[\\\/]",
                  r"^cloud_print[\\\/]",