Remove seemingly unnecessary element continuation child logic

This logic doesn't make a difference in any tests.
Notably: continuation.html in web tests passes.

This CL progresses towards removal of
ShouldUseLayoutBuilderTraversal(), simplifying AddChildren() and
removing conditions that lead to lack of symmetry in
child-parent relationships.

Bug: None
Change-Id: Ic436c4dd51ba7d12cd6adec0f7d35cdbab7dc487
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2563863Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832024}

content/browser/accessibility/dump_accessibility_tree_browsertest.cc

@@ -595,6 +595,10 @@ IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest,
   RunAriaTest(FILE_PATH_LITERAL("aria-contentinfo.html"));
 }
 
+IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityContinuations) {
+  RunHtmlTest(FILE_PATH_LITERAL("continuations.html"));
+}
+
 IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityAriaControls) {
   RunAriaTest(FILE_PATH_LITERAL("aria-controls.html"));
 }

content/test/data/accessibility/html/continuations-expected-auralinux.txt

+[document web]
+++[panel] name='Group 1'
+++++[section]
+++++++[push button] name='Before'
+++++[section]
+++++++[static] name='After'
+++[panel] name='Group 2'
+++++[section]
+++++++[static] name='Before'
+++++[section]
+++++++[static] name='After'
+++[panel] name='Group 3'
+++++[link] name='Before'
+++++++[section]
+++++++++[static] name='Before'
+++++[section]
+++++++[link] name='Ever '
+++++++++[static] name='Ever '
+++++++[link] name='After'
+++++++++[static] name='After'
+++[panel] name='Group 4'
+++++[section]
+++++++[static] name='Before'
+++++[paragraph]
+++++++[static] name='After'
+++[panel] name='Group 5'
+++++[static] name='Italic only '
+++++[static] name='italic and bold'
+++++[section]
+++++++[static] name='Wow, a block!'
+++++[section]
+++++++[static] name='Wow, another block!'
+++++[static] name='More italic and bold text'
+++++[static] name=' More italic text'

content/test/data/accessibility/html/continuations-expected-blink.txt

+rootWebArea isLineBreakingObject=true
+++genericContainer ignored display='block' isLineBreakingObject=true
+++++genericContainer ignored display='block' isLineBreakingObject=true
+++++++group display='block' name='Group 1' isLineBreakingObject=true
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++button display='inline-block' name='Before' isLineBreakingObject=true
+++++++++++++staticText display='inline-block' name='Before'
+++++++++++++++inlineTextBox display='inline-block' name='Before'
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++staticText display='block' name='After'
+++++++++++++inlineTextBox display='block' name='After'
+++++++group display='block' name='Group 2' isLineBreakingObject=true
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++staticText display='block' name='Before'
+++++++++++++inlineTextBox display='block' name='Before'
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++staticText display='block' name='After'
+++++++++++++inlineTextBox display='block' name='After'
+++++++group display='block' name='Group 3' isLineBreakingObject=true
+++++++++anchor display='inline' name='Before'
+++++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++++staticText display='block' name='Before'
+++++++++++++++inlineTextBox display='block' name='Before'
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++anchor display='inline' name='Ever '
+++++++++++++staticText display='inline' name='Ever '
+++++++++++++++inlineTextBox display='inline' name='Ever '
+++++++++++link display='inline' name='After'
+++++++++++++staticText display='inline' name='After'
+++++++++++++++inlineTextBox display='inline' name='After'
+++++++group display='block' name='Group 4' isLineBreakingObject=true
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++staticText display='block' name='Before'
+++++++++++++inlineTextBox display='block' name='Before'
+++++++++genericContainer ignored display='block' isLineBreakingObject=true
+++++++++++paragraph display='block' isLineBreakingObject=true
+++++++++++++staticText display='block' name='After'
+++++++++++++++inlineTextBox display='block' name='After'
+++++++group display='block' name='Group 5' isLineBreakingObject=true
+++++++++staticText display='inline' name='Italic only '
+++++++++++inlineTextBox display='inline' name='Italic only '
+++++++++staticText display='inline' name='italic and bold'
+++++++++++inlineTextBox display='inline' name='italic and bold'
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++staticText display='block' name='Wow, a block!'
+++++++++++++inlineTextBox display='block' name='Wow, a block!'
+++++++++genericContainer display='block' isLineBreakingObject=true
+++++++++++staticText display='block' name='Wow, another block!'
+++++++++++++inlineTextBox display='block' name='Wow, another block!'
+++++++++staticText display='inline' name='More italic and bold text'
+++++++++++inlineTextBox display='inline' name='More italic and bold text'
+++++++++staticText display='inline' name=' More italic text'
+++++++++++inlineTextBox display='inline' name=' More italic text'

content/test/data/accessibility/html/continuations.html

+<!--
+@BLINK-ALLOW:display*
+@BLINK-ALLOW:isLineBreakingObject*
+-->
+<!--
+Continuations in Blink are described here:
+https://webkit.org/blog/115/webcore-rendering-ii-blocks-and-inlines/
+-->
+<div role="group" aria-label="Group 1">
+  <b>
+  <i>
+    <div>
+      <button id="before">Before</button>
+    </div></i><div id="after">After</div></b>
+</div>
+
+<div role="group" aria-label="Group 2">
+  <foo>
+    <bar>
+      <div id="before">Before</div>
+    </bar><div id="after">After</div>
+  </foo>
+</div>
+
+<div role="group" aria-label="Group 3">
+  <span>
+    <a name="a">
+      <div id="before">Before</div>
+      <div id="ever">
+        Ever
+        <a href="#" id="after">After</a>
+      </div>
+    </a>
+  </span>
+</div>
+
+<div role="group" aria-label="Group 4">
+  <div id="before">Before</div>
+  <div><span><p id="after">After</p></span></div>
+</div>
+
+<div role="group" aria-label="Group 5">
+  <i>Italic only <b>italic and bold
+  <div>
+  Wow, a block!
+  </div>
+  <div>
+  Wow, another block!
+  </div>
+  More italic and bold text</b> More italic text</i>
+</div>

third_party/blink/renderer/modules/accessibility/ax_node_object.cc

@@ -3227,10 +3227,6 @@ bool AXNodeObject::ShouldUseLayoutBuilderTraversal() const {
   // it's possible for the same object to become a child of 2 different nodes,
   // e.g. if it has a different layout parent and DOM parent.
 
-  // Avoid calling AXNodeObject logic for continuations.
-  if (GetLayoutObject() && GetLayoutObject()->IsElementContinuation())
-    return false;
-
   Node* node = GetNode();
   if (!node)
     return false;