Enable download_protection_service_unittest.cc on ChromeOS

Enabling the tests was missed in https://codereview.chromium.org/10970023.

BUG=127046

Review URL: https://codereview.chromium.org/1012263002

Cr-Commit-Position: refs/heads/master@{#321843}

chrome/chrome_tests_unit.gypi

@@ -2316,11 +2316,6 @@
             'ipc_protobuf_message_test_proto',
           ],
           'conditions': [
-            ['chromeos == 1', {
-              'sources!': [
-                'browser/safe_browsing/download_protection_service_unittest.cc',
-              ],
-            }],
             ['OS == "android"', {
               'dependencies!': [
                 'ipc_protobuf_message_test_proto',

chrome/test/BUILD.gn

@@ -1441,9 +1441,7 @@ if (!is_android) {
               "//chrome")
       defines += [ "FULL_SAFE_BROWSING" ]
       deps += [ ":test_proto" ]
-      if (is_chromeos) {
-        sources -= [ "../browser/safe_browsing/download_protection_service_unittest.cc" ]
-      } else if (is_android) {
+      if (is_android) {
         deps -= [ ":test_proto" ]
         sources -= [
           # Android doesn't support download feedbacks.