Remove LayoutNGFragmentItem runtime flag

This patch removes |LayoutNGFragmentItem| runtime flag and
|FragmentItem| feature.

These flags are already on by default in stable.

Bug: 1154531
Change-Id: I68bdd1e2cac5a32c69eba6d5cbff26b798ddab63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2629331
Commit-Queue: Kent Tamura <tkent@chromium.org>
Auto-Submit: Koji Ishii <kojii@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843949}

content/child/runtime_features.cc

@@ -366,7 +366,6 @@ void SetRuntimeFeaturesFromChromiumFeatures() {
           {"LayoutNG", blink::features::kLayoutNG},
           {"LayoutNGTable", blink::features::kLayoutNGTable},
           {"LayoutNGFieldset", blink::features::kLayoutNGFieldset},
-          {"LayoutNGFragmentItem", blink::features::kFragmentItem},
           {"LayoutNGTextControl", blink::features::kLayoutNGTextControl},
           {"LegacyWindowsDWriteFontFallback",
            features::kLegacyWindowsDWriteFontFallback},

third_party/blink/common/features.cc

@@ -105,9 +105,6 @@ const base::Feature kLayoutNGFieldset{"LayoutNGFieldset",
 const base::Feature kLayoutNGTextControl{"LayoutNGTextControl",
                                          base::FEATURE_DISABLED_BY_DEFAULT};
 
-const base::Feature kFragmentItem{"FragmentItem",
-                                  base::FEATURE_ENABLED_BY_DEFAULT};
-
 const base::Feature kMixedContentAutoupgrade{"AutoupgradeMixedContent",
                                              base::FEATURE_ENABLED_BY_DEFAULT};
 

third_party/blink/public/common/features.h

@@ -41,7 +41,6 @@ BLINK_COMMON_EXPORT extern const base::Feature kLayoutNG;
 BLINK_COMMON_EXPORT extern const base::Feature kLayoutNGTable;
 BLINK_COMMON_EXPORT extern const base::Feature kLayoutNGFieldset;
 BLINK_COMMON_EXPORT extern const base::Feature kLayoutNGTextControl;
-BLINK_COMMON_EXPORT extern const base::Feature kFragmentItem;
 BLINK_COMMON_EXPORT extern const base::Feature kMixedContentAutoupgrade;
 BLINK_COMMON_EXPORT extern const base::Feature kNavigationPredictor;
 BLINK_COMMON_EXPORT extern const base::Feature kParentNodeReplaceChildren;

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1085,11 +1085,6 @@
       depends_on: ["LayoutNG"],
       status: "stable",
     },
-    {
-      name: "LayoutNGFragmentItem",
-      implied_by: ["LayoutNGBlockFragmentation", "LayoutNGFragmentTraversal", "EditingNG"],
-      status: "stable",
-    },
     {
       // Traverse the fragment tree when painting and hit-testing, instead of
       // the layout object tree.
@@ -1107,7 +1102,7 @@
     },
     {
       name: "LayoutNGLayoutOverflow",
-      depends_on: ["LayoutNG", "LayoutNGFragmentItem"],
+      depends_on: ["LayoutNG"],
       status: "stable",
     },
     {