LibWeb: Process style sheets in document order

Until now we would simply apply stylesheets in the order they finished
loading. This patch adds a StyleSheetList object that hangs off of each
Document and contains all the style sheets in document order.

There's still a lot of work to do for a proper cascade, but at least
this makes us consistently wrong every time. :^)

Libraries/LibWeb/CSS/StyleResolver.cpp

@@ -60,7 +60,7 @@ template<typename Callback>
 void StyleResolver::for_each_stylesheet(Callback callback) const
 {
     callback(default_stylesheet());
-    for (auto& sheet : document().stylesheets()) {
+    for (auto& sheet : document().style_sheets().sheets()) {
         callback(sheet);
     }
 }

Libraries/LibWeb/CSS/StyleSheet.h

@@ -41,6 +41,7 @@ public:
     ~StyleSheet();
 
     const NonnullRefPtrVector<StyleRule>& rules() const { return m_rules; }
+    NonnullRefPtrVector<StyleRule>& rules() { return m_rules; }
 
 private:
     explicit StyleSheet(NonnullRefPtrVector<StyleRule>&&);

Libraries/LibWeb/CSS/StyleSheetList.cpp

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibWeb/CSS/StyleSheetList.h>
+
+namespace Web {
+namespace CSS {
+
+void StyleSheetList::add_sheet(NonnullRefPtr<StyleSheet> sheet)
+{
+    m_sheets.append(move(sheet));
+}
+
+StyleSheetList::StyleSheetList(Document& document)
+    : m_document(document)
+{
+}
+
+}
+}

Libraries/LibWeb/CSS/StyleSheetList.h

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <LibWeb/CSS/StyleSheet.h>
+
+namespace Web {
+namespace CSS {
+
+class StyleSheetList : public RefCounted<StyleSheetList> {
+public:
+    static NonnullRefPtr<StyleSheetList> create(Document& document)
+    {
+        return adopt(*new StyleSheetList(document));
+    }
+
+    void add_sheet(NonnullRefPtr<StyleSheet>);
+
+    const NonnullRefPtrVector<StyleSheet>& sheets() const { return m_sheets; }
+
+private:
+    explicit StyleSheetList(Document&);
+
+    Document& m_document;
+    NonnullRefPtrVector<StyleSheet> m_sheets;
+};
+
+}
+}