Imply LayoutNGFragmentItem with LayoutNGBlockFragmentation.

Some block fragmentation unit tests had to be "rebaselined", since we
don't see fragments inside lines anymore.

Also skip virtual layout_ng_block_frag and layout_ng_fieldset tests
when NG is disabled. There's something weird going on with the
feature implication mechanism, but running these tests when NG is
disabled is pretty meaningless anyway.

Bug: 829028, 982194
Change-Id: Ia5e860145cb348425d6171ba624e80c25090983b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2102648
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750494}

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -906,7 +906,7 @@
     },
     {
       name: "LayoutNGFragmentItem",
-      implied_by: ["LayoutNGFragmentTraversal"],
+      implied_by: ["LayoutNGBlockFragmentation", "LayoutNGFragmentTraversal"],
     },
     {
       name: "LayoutNGFragmentPaint",

third_party/blink/web_tests/FlagExpectations/disable-layout-ng

@@ -373,6 +373,12 @@ virtual/controls-refresh-hc/* [ Skip ]
 ### virtual/form-controls-refresh-disabled/
 virtual/form-controls-refresh-disabled/* [ Skip ]
 
+### virtual/layout_ng_block_frag/
+virtual/layout_ng_block_frag/* [ Skip ]
+
+### virtual/layout_ng_fieldset/
+virtual/layout_ng_fieldset/* [ Skip ]
+
 ### virtual/layout_ng_fragment_traversal/
 virtual/layout_ng_fragment_traversal/* [ Skip ]
 
@@ -463,7 +469,6 @@ svg/zoom/text/zoom-svg-float-border-padding.xml [ Failure ]
 virtual/composite-after-paint/scrollingcoordinator/non-fast-scrollable-transform-changed.html [ Crash ]
 virtual/forced-high-contrast-colors/fast/css/forced-colors-mode/forced-colors-mode-15.html [ Failure ]
 virtual/forced-high-contrast-colors/fast/css/forced-colors-mode/backplate/forced-colors-mode-backplate-07.html [ Failure ]
-virtual/layout_ng_block_frag/external/wpt/css/css-break/hit-test-inline-fragmentation-with-border-radius.html [ Failure ]
 
 
 # 10/27/2019 updates.

third_party/blink/web_tests/VirtualTestSuites

@@ -196,7 +196,7 @@
               "fast/multicol",
               "fragmentation",
               "printing"],
-    "args": ["--enable-blink-features=LayoutNGBlockFragmentation,LayoutNGFieldset,LayoutNGFragmentItem"]
+    "args": ["--enable-blink-features=LayoutNGBlockFragmentation,LayoutNGFieldset"]
   },
   {
     "prefix": "layout_ng_fragment_traversal",