LibHTML: Add load(URL) and reload() functions to HtmlView

You can now pass a file:/// URL to HtmlView and it will take care of
the loading logic for you. Each Document remembers the URL it was
loaded from, which allows us to also have reload().

This patch also adds a very simple function for resolving relative
URL's into absolute ones.

Libraries/LibHTML/HtmlView.cpp

@@ -1,3 +1,4 @@
+#include <LibCore/CFile.h>
 #include <LibGUI/GApplication.h>
 #include <LibGUI/GPainter.h>
 #include <LibGUI/GScrollBar.h>
@@ -7,6 +8,7 @@
 #include <LibHTML/Frame.h>
 #include <LibHTML/HtmlView.h>
 #include <LibHTML/Layout/LayoutNode.h>
+#include <LibHTML/Parser/HTMLParser.h>
 #include <LibHTML/RenderingContext.h>
 #include <stdio.h>
 
@@ -147,3 +149,30 @@ void HtmlView::mousedown_event(GMouseEvent& event)
         update();
     event.accept();
 }
+
+void HtmlView::reload()
+{
+    load(main_frame().document()->url());
+}
+
+void HtmlView::load(const URL& url)
+{
+    dbg() << "HtmlView::load: " << url;
+
+    if (on_load_start)
+        on_load_start(url);
+
+    auto f = CFile::construct();
+    f->set_filename(url.path());
+    if (!f->open(CIODevice::OpenMode::ReadOnly)) {
+        dbg() << "HtmlView::load: Error: " << f->error_string();
+        return;
+    }
+
+    String html = String::copy(f->read_all());
+    auto document = parse_html(html);
+    document->set_url(url);
+    document->normalize();
+
+    set_document(document);
+}