[FlexNG] Teach test harness "LayoutNGFlexibleBox"

Now it won't fail when it expects LayoutFlexibleBox but sees
LayoutNGFlexibleBox

Fixes
compositing/video/video-poster.html
paint/invalidation/video-paint-invalidation.html
paint/invalidation/image/canvas-composite-repaint-by-all-imagesource.html
virtual/android/fullscreen/video-overlay-scroll.html

Bug: 845235
Change-Id: I7cad9787294e8f0b9cf233c769028c1bc571c507
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2053423Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: David Grogan <dgrogan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741140}

third_party/blink/tools/blinkpy/web_tests/controllers/single_test_runner.py

@@ -427,15 +427,14 @@ class SingleTestRunner(object):
             return text
 
         def remove_ng_text(results):
-            processed = re.sub(
-                r'LayoutNG(BlockFlow|ListItem|TableCell)', r'Layout\1', results)
+            processed = re.sub(r'LayoutNG(BlockFlow|ListItem|TableCell|FlexibleBox)', r'Layout\1', results)
             # LayoutTableCaption doesn't override LayoutBlockFlow::GetName, so
             # render tree dumps have "LayoutBlockFlow" for captions.
             processed = re.sub('LayoutNGTableCaption', 'LayoutBlockFlow', processed)
             return processed
 
         def is_ng_name_mismatch(expected, actual):
-            if not re.search("LayoutNG(BlockFlow|ListItem|TableCaption|TableCell)", actual):
+            if not re.search("LayoutNG(BlockFlow|ListItem|TableCaption|TableCell|FlexibleBox)", actual):
                 return False
             if not self._is_render_tree(actual) and not self._is_layer_tree(actual):
                 return False