[webkitpy] Treat LayoutNG name mismatch as PASS

This patch changes the layout test runner to treat LayoutNG name
mismatch (e.g., LayoutBlockFlow vs. LayoutNGBlockFlow) as PASS instead
of TEXT failure, to reduce noise in test result.

Bug: 795043
Change-Id: Ia0a358f7ccf47cc809fff6b20eea1847d4754413
Reviewed-on: https://chromium-review.googlesource.com/828276Reviewed-by: Aleks Totic <atotic@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524407}

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/single_test_runner.py

@@ -357,9 +357,10 @@ class SingleTestRunner(object):
             processed = actual.replace('LayoutNGBlockFlow', 'LayoutBlockFlow').replace('LayoutNGListItem', 'LayoutListItem')
             return not self._port.do_text_results_differ(expected, processed)
 
-        # LayoutNG name mismatch
+        # LayoutNG name mismatch (e.g., LayoutBlockFlow vs. LayoutNGBlockFlow)
+        # is treated as pass
         if is_ng_name_mismatch(expected_text, normalized_actual_text):
-            return [test_failures.FailureLayoutNGNameMismatch()]
+            return []
 
         # General text mismatch
         if self._port.do_text_results_differ(

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/models/test_failures.py

@@ -216,15 +216,6 @@ class FailureSpaceTabLineBreakTextMismatch(FailureTextMismatch):
         return 'spaces, tabs and newlines only'
 
 
-class FailureLayoutNGNameMismatch(FailureTextMismatch):
-
-    def message(self):
-        return 'text diff due to LayoutNG name mismatch'
-
-    def text_mismatch_category(self):
-        return 'LayoutNG name mismatch'
-
-
 class FailureMissingImageHash(TestFailure):
 
     def message(self):
@@ -313,7 +304,7 @@ ALL_FAILURE_CLASSES = (FailureTimeout, FailureCrash, FailureMissingResult,
                        FailureTestHarnessAssertion,
                        FailureTextMismatch, FailureSpacesAndTabsTextMismatch,
                        FailureLineBreaksTextMismatch, FailureSpaceTabLineBreakTextMismatch,
-                       FailureLayoutNGNameMismatch, FailureMissingImageHash,
+                       FailureMissingImageHash,
                        FailureMissingImage, FailureImageHashMismatch,
                        FailureImageHashIncorrect, FailureReftestMismatch,
                        FailureReftestMismatchDidNotOccur,