Fix for ::selection pseudo element to work on input elements

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index 36cc3c3a510e50dfaeb972df4d7b9afffce99ba7..34d9465d34a710ac7a5fcc30922b544210b208aa 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -1787,6 +1787,17 @@ Color RenderObject::selectionBackgroundColor() const
 
     if (RefPtr<RenderStyle> pseudoStyle = getUncachedPseudoStyle(PseudoStyleRequest(SELECTION)))
         return resolveColor(pseudoStyle.get(), CSSPropertyBackgroundColor).blendWithWhite();
+
+    // If the element is in shadow tree of input element, then get the PseudoStyle
+    // from the input element.
+    if (node() && node()->shadowHost()) {
+        RenderObject* shadowHostRenderer = node()->shadowHost()->renderer();
+        if (shadowHostRenderer->isTextControl()) {

[ojan, 2014/04/09 01:57:53]

Special casing text controls is not right. For example, this won't fix buttons:
<input type="button" value="button" style="-webkit-user-select:auto">

Also, the way I would expect this code to work is that you'd set the pseudoStyle
based of whether it's in a shadowHost. That way you wouldn't need to duplicate
the resolveColor line.

That all said, I'm not really sure what the right fix is. I defer to
tkent/esprehn on what the right way to target user-agent shadow hosts is.

+            if (RefPtr<RenderStyle> pseudoStyle = shadowHostRenderer->getUncachedPseudoStyle(PseudoStyleRequest(SELECTION)))
+                return resolveColor(pseudoStyle.get(), CSSPropertyBackgroundColor).blendWithWhite();
+        }
+    }
+
     return frame()->selection().isFocusedAndActive() ?
         RenderTheme::theme().activeSelectionBackgroundColor() :
         RenderTheme::theme().inactiveSelectionBackgroundColor();
@@ -1801,6 +1812,17 @@ Color RenderObject::selectionColor(int colorProperty) const
 
     if (RefPtr<RenderStyle> pseudoStyle = getUncachedPseudoStyle(PseudoStyleRequest(SELECTION)))
         return resolveColor(pseudoStyle.get(), colorProperty);
+
+    // If the element is in shadow tree of input element, then get the PseudoStyle
+    // from the input element.
+    if (node() && node()->shadowHost()) {
+        RenderObject* shadowHostRenderer = node()->shadowHost()->renderer();
+        if (shadowHostRenderer->isTextControl()) {
+            if (RefPtr<RenderStyle> pseudoStyle = shadowHostRenderer->getUncachedPseudoStyle(PseudoStyleRequest(SELECTION)))
+                return resolveColor(pseudoStyle.get(), colorProperty);
+        }
+    }
+
     if (!RenderTheme::theme().supportsSelectionForegroundColors())
         return resolveColor(colorProperty);
     return frame()->selection().isFocusedAndActive() ?