[LayoutNG] Change how content editable forces legacy layout

This patch changes how editing forces legacy layout to the one
added for form controls[1] to use legacy layout tree for nested editable, e.g.
  <div contenteditable>
  legacy layout tree
    <div contenteditable=false>
      non-editable block in editable block should be legacy
    </div>
  </div>

This patch continues http://crrev.com/c/880542

[1] http://crrev.com/c/875511 Change form controls not to use LayoutNG

Bug: 714962
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I78d44fc82b3de5e647b67ee6aa7733db62e344b8
Reviewed-on: https://chromium-review.googlesource.com/880530
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531861}

third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp

@@ -640,19 +640,21 @@ void StyleAdjuster::AdjustComputedStyle(StyleResolverState& state,
     }
   }
 
-  if (RuntimeEnabledFeatures::LayoutNGEnabled()) {
+  if (RuntimeEnabledFeatures::LayoutNGEnabled() && !style.ForceLegacyLayout()) {
     // Form controls are not supported yet.
-    if (!style.ForceLegacyLayout() && element &&
-        element->ShouldForceLegacyLayout()) {
+    if (element && element->ShouldForceLegacyLayout()) {
       style.SetForceLegacyLayout(true);
     }
 
     // TODO(layout-dev): Once LayoutNG handles inline content editable, we
     // should get rid of following code fragment.
-    else if (style.UserModify() != EUserModify::kReadOnly &&
-             style.Display() == EDisplay::kInline &&
-             parent_style.UserModify() == EUserModify::kReadOnly) {
-      style.SetDisplay(EDisplay::kInlineBlock);
+    else if (style.UserModify() != EUserModify::kReadOnly) {
+      style.SetForceLegacyLayout(true);
+
+      if (style.Display() == EDisplay::kInline &&
+          parent_style.UserModify() == EUserModify::kReadOnly) {
+        style.SetDisplay(EDisplay::kInlineBlock);
+      }
     }
   }
 }

third_party/WebKit/Source/core/editing/LayoutSelectionTest.cpp

@@ -820,6 +820,7 @@ TEST_F(NGLayoutSelectionTest, MixedBlockFlowsAsSibling) {
 }
 
 TEST_F(NGLayoutSelectionTest, MixedBlockFlowsAnscestor) {
+  // Both "foo" and "bar" for DIV elements should be legacy LayoutBlock.
   const SelectionInDOMTree& selection = SetSelectionTextToBody(
       "<div contenteditable>f^oo"
       "<div contenteditable=false>ba|r</div></div>");
@@ -829,19 +830,10 @@ TEST_F(NGLayoutSelectionTest, MixedBlockFlowsAnscestor) {
   TEST_NEXT(IsLegacyBlockFlow, kContain, NotInvalidate);
   TEST_NEXT(IsLayoutNGBlockFlow, kContain, NotInvalidate);
   TEST_NEXT("foo", kStart, ShouldInvalidate);
-  TEST_NEXT(IsLayoutNGBlockFlow, kContain, NotInvalidate);
+  TEST_NEXT(IsLegacyBlockFlow, kContain, NotInvalidate);
   TEST_NEXT("bar", kEnd, ShouldInvalidate);
   TEST_NO_NEXT_LAYOUT_OBJECT();
   EXPECT_EQ(1u, Selection().LayoutSelectionStart().value());
-  LayoutObject* const bar = GetDocument()
-                                .body()
-                                ->firstChild()
-                                ->firstChild()
-                                ->nextSibling()
-                                ->firstChild()
-                                ->GetLayoutObject();
-  EXPECT_EQ(std::make_pair(0u, 2u), Selection().LayoutSelectionStartEndForNG(
-                                        GetNGPhysicalTextFragment(bar)));
 }
 
 TEST_F(NGLayoutSelectionTest, MixedBlockFlowsDecendant) {

third_party/WebKit/Source/core/layout/LayoutObject.cpp

@@ -113,8 +113,7 @@ static bool g_modify_layout_tree_structure_any_state = false;
 
 inline bool ShouldUseNewLayout(const ComputedStyle& style) {
   return RuntimeEnabledFeatures::LayoutNGEnabled() &&
-         !style.ForceLegacyLayout() &&
-         style.UserModify() == EUserModify::kReadOnly;
+         !style.ForceLegacyLayout();
 }
 
 template <typename Predicate>