Ladybird: Start applying the default content filter

For the first cut, the file path is not configurable and the content
filter cannot be toggled on or off. If we fail to apply the content
filters for any reason (e.g. the filter file doesn't exist), we simply
just stop loading the content filters to allow using Ladybird without
content filters.

Ladybird/SimpleWebView.cpp

@@ -49,6 +49,7 @@
 #include <LibWeb/HTML/Storage.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/Layout/InitialContainingBlock.h>
+#include <LibWeb/Loader/ContentFilter.h>
 #include <LibWeb/Loader/ResourceLoader.h>
 #include <LibWeb/Page/Page.h>
 #include <LibWeb/Painting/PaintableBox.h>
@@ -432,6 +433,19 @@ static void platform_init()
 #endif
 }
 
+static ErrorOr<void> load_content_filters()
+{
+    auto file = TRY(Core::Stream::File::open(String::formatted("{}/home/anon/.config/BrowserContentFilters.txt", s_serenity_resource_root), Core::Stream::OpenMode::Read));
+    auto ad_filter_list = TRY(Core::Stream::BufferedFile::create(move(file)));
+    auto buffer = TRY(ByteBuffer::create_uninitialized(4096));
+    while (TRY(ad_filter_list->can_read_line())) {
+        auto line = TRY(ad_filter_list->read_line(buffer));
+        if (!line.is_empty())
+            Web::ContentFilter::the().add_pattern(line);
+    }
+    return {};
+}
+
 void initialize_web_engine()
 {
     platform_init();
@@ -447,6 +461,10 @@ void initialize_web_engine()
     Web::Platform::FontPlugin::install(*new Ladybird::FontPluginQt);
 
     Web::FrameLoader::set_error_page_url(String::formatted("file://{}/res/html/error.html", s_serenity_resource_root));
+
+    auto maybe_content_filter_error = load_content_filters();
+    if (maybe_content_filter_error.is_error())
+        dbgln("Failed to load content filters: {}", maybe_content_filter_error.error());
 }
 
 void SimpleWebView::debug_request(String const& request, String const& argument)