[Squad] Make kPseudoIdFirstLineInherited an internal pseudo.

Gets rid of MutableStyleRef() access where we called SetHasPseudo() for
the inherited first-line styles in order to not return early from
GetCachedPseudoStyle.

TEST=fast/css/invalidation/first-line-change-inline-color-inherited.html

Bug: 813068
Change-Id: Ib34d8ae23e6203ccb27511fb3f5580d8d3002500
Reviewed-on: https://chromium-review.googlesource.com/1059249Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558831}

third_party/blink/renderer/core/css/ComputedStyleExtraFields.json5

@@ -196,7 +196,7 @@
     {
       name: "PseudoBits",
       field_template: "primitive",
-      field_size: 8,
+      field_size: 7,
       default_value: "kPseudoIdNone",
       type_name: "unsigned",
       custom_copy: true,

third_party/blink/renderer/core/layout/layout_object.cc

@@ -3400,8 +3400,6 @@ static scoped_refptr<ComputedStyle> FirstLineStyleForCachedUncachedType(
       if (type == kCached) {
         // A first-line style is in effect. Cache a first-line style for
         // ourselves.
-        layout_object_for_first_line_style->MutableStyleRef().SetHasPseudoStyle(
-            kPseudoIdFirstLineInherited);
         return layout_object_for_first_line_style->GetCachedPseudoStyle(
             kPseudoIdFirstLineInherited, parent_style);
       }

third_party/blink/renderer/core/style/computed_style_constants.h

@@ -63,8 +63,8 @@ enum StyleRecalcChange {
 // Static pseudo styles. Dynamic ones are produced on the fly.
 enum PseudoId {
   // The order must be NOP ID, public IDs, and then internal IDs.
-  // If you add or remove a public ID, you must update _pseudoBits in
-  // ComputedStyle.
+  // If you add or remove a public ID, you must update the field_size of
+  // "PseudoBits" in ComputedStyleExtraFields.json5.
   kPseudoIdNone,
   kPseudoIdFirstLine,
   kPseudoIdFirstLetter,
@@ -72,9 +72,9 @@ enum PseudoId {
   kPseudoIdAfter,
   kPseudoIdBackdrop,
   kPseudoIdSelection,
-  kPseudoIdFirstLineInherited,
   kPseudoIdScrollbar,
   // Internal IDs follow:
+  kPseudoIdFirstLineInherited,
   kPseudoIdScrollbarThumb,
   kPseudoIdScrollbarButton,
   kPseudoIdScrollbarTrack,
@@ -85,7 +85,7 @@ enum PseudoId {
   // Special values follow:
   kAfterLastInternalPseudoId,
   kFirstPublicPseudoId = kPseudoIdFirstLine,
-  kFirstInternalPseudoId = kPseudoIdScrollbarThumb,
+  kFirstInternalPseudoId = kPseudoIdFirstLineInherited,
   kElementPseudoIdMask = (1 << (kPseudoIdBefore - kFirstPublicPseudoId)) |
                          (1 << (kPseudoIdAfter - kFirstPublicPseudoId)) |
                          (1 << (kPseudoIdBackdrop - kFirstPublicPseudoId))