Implement the ::backdrop pseudo-element for modal <dialog>.

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index c72643e50dc939b355312672aab8077f2b6b0d7e..1c89f9c765bea8bd2ba16a4699d00bd37d4b82e8 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -1229,7 +1229,7 @@ PassRefPtr<RenderStyle> StyleResolver::pseudoStyleForElement(Element* e, const P
 
     state.initForStyleResolve(document(), e, parentStyle);
 
-    if (m_state.parentStyle()) {
+    if (pseudoStyleRequest.pseudoId != BACKDROP && m_state.parentStyle()) { // The spec disallows inheritance for ::backdrop.

[esprehn, 2013/07/03 23:44:29]

Lets add a method on PseudoStyleRequest which is allowsInheritance() const {
return parentStyle() && pseudoId != BACKDROP; }

btw I don't think this is enough, adjustRenderStyle below is going to muck up
your style based on your parentStyle even though you're being reparented into
the render view. This is a general issue, I think you need to fix
adjustRenderStyle to be smarter for top layer. Lets fix that in a different
patch though, it's only a few cases where you can tell.

[falken, 2013/07/04 08:20:12]

Done. That looks a lot better.
OK thanks, will take a look.

         state.setStyle(RenderStyle::create());
         state.style()->inheritFrom(m_state.parentStyle());
     } else {
@@ -1403,13 +1403,17 @@ static EDisplay equivalentBlockDisplay(EDisplay display, bool isFloating, bool s
 // CSS requires text-decoration to be reset at each DOM element for tables,
 // inline blocks, inline tables, run-ins, shadow DOM crossings, floating elements,
 // and absolute or relatively positioned elements.
-static bool doesNotInheritTextDecoration(RenderStyle* style, Element* e)
+static bool doesNotInheritTextDecoration(const RenderStyle* style, const Element* e)
 {
     return style->display() == TABLE || style->display() == INLINE_TABLE || style->display() == RUN_IN
         || style->display() == INLINE_BLOCK || style->display() == INLINE_BOX || isAtShadowBoundary(e)
         || style->isFloating() || style->hasOutOfFlowPosition();
 }
 
+static bool isRenderedInTopLayer(const RenderStyle* style, const Element* e) {
+    return (e && e->isInTopLayer()) || (style && style->styleType() == BACKDROP);

[esprehn, 2013/07/03 23:44:29]

This looks bad, the PseudoElement for ::backdrop should have isInTopLayer as
true. By design PseudoElements should act like real elements with the same bits
set on them.

[falken, 2013/07/04 08:20:12]

Even with the new patch, I have to keep this helper since we enter
adjustRenderStyle as part of createPseudoElementIfNeeded, so the element is
null.

+}
+
 static bool isDisplayFlexibleBox(EDisplay display)
 {
     return display == FLEX || display == INLINE_FLEX;
@@ -1478,7 +1482,7 @@ void StyleResolver::adjustRenderStyle(RenderStyle* style, RenderStyle* parentSty
             style->setDisplay(BLOCK);
 
         // Per the spec, position 'static' and 'relative' in the top layer compute to 'absolute'.
-        if (e && e->isInTopLayer() && (style->position() == StaticPosition || style->position() == RelativePosition))
+        if (isRenderedInTopLayer(style, e) && (style->position() == StaticPosition || style->position() == RelativePosition))
             style->setPosition(AbsolutePosition);
 
         // Absolute/fixed positioned elements, floating elements and the document element need block-like outside display.
@@ -1534,7 +1538,7 @@ void StyleResolver::adjustRenderStyle(RenderStyle* style, RenderStyle* parentSty
         || style->hasBlendMode()
         || style->position() == StickyPosition
         || (style->position() == FixedPosition && e && e->document()->page() && e->document()->page()->settings()->fixedPositionCreatesStackingContext())
-        || (e && e->isInTopLayer())
+        || isRenderedInTopLayer(style, e)
         ))
         style->setZIndex(0);