LibWeb+LibWebView+WebContent: Add support for <input type="color">

This commit introduces 3 things:
- Support for the color type in HTMLInputElement itself
- A mechanism for handling non event loop blocking dialogs in Page
- The associated plumbing up to ViewImplementation

Frontends may add support for the color picker with the
ViewImplementation.on_request_color_picker function

Userland/Services/WebContent/ConnectionFromClient.cpp

@@ -892,6 +892,11 @@ void ConnectionFromClient::prompt_closed(Optional<String> const& response)
     m_page_host->prompt_closed(response);
 }
 
+void ConnectionFromClient::color_picker_closed(Optional<Color> const& picked_color)
+{
+    m_page_host->color_picker_closed(picked_color);
+}
+
 void ConnectionFromClient::toggle_media_play_state()
 {
     m_page_host->toggle_media_play_state().release_value_but_fixme_should_propagate_errors();

Userland/Services/WebContent/ConnectionFromClient.h

@@ -97,6 +97,7 @@ private:
     virtual void alert_closed() override;
     virtual void confirm_closed(bool accepted) override;
     virtual void prompt_closed(Optional<String> const& response) override;
+    virtual void color_picker_closed(Optional<Color> const& picked_color) override;
 
     virtual void toggle_media_play_state() override;
     virtual void toggle_media_mute_state() override;

Userland/Services/WebContent/PageHost.cpp

@@ -358,6 +358,11 @@ void PageHost::prompt_closed(Optional<String> response)
     page().prompt_closed(move(response));
 }
 
+void PageHost::color_picker_closed(Optional<Color> picked_color)
+{
+    page().color_picker_closed(picked_color);
+}
+
 Web::WebIDL::ExceptionOr<void> PageHost::toggle_media_play_state()
 {
     return page().toggle_media_play_state();
@@ -453,4 +458,9 @@ void PageHost::request_file(Web::FileRequest file_request)
     m_client.request_file(move(file_request));
 }
 
+void PageHost::page_did_request_color_picker(Color current_color)
+{
+    m_client.async_did_request_color_picker(current_color);
+}
+
 }

Userland/Services/WebContent/PageHost.h

@@ -48,6 +48,7 @@ public:
     void alert_closed();
     void confirm_closed(bool accepted);
     void prompt_closed(Optional<String> response);
+    void color_picker_closed(Optional<Color> picked_color);
 
     Web::WebIDL::ExceptionOr<void> toggle_media_play_state();
     void toggle_media_mute_state();
@@ -113,6 +114,7 @@ private:
     virtual void page_did_request_activate_tab() override;
     virtual void page_did_close_browsing_context(Web::HTML::BrowsingContext const&) override;
     virtual void request_file(Web::FileRequest) override;
+    virtual void page_did_request_color_picker(Color current_color) override;
     virtual void page_did_finish_text_test() override;
 
     explicit PageHost(ConnectionFromClient&);

Userland/Services/WebContent/WebContentClient.ipc

@@ -59,6 +59,7 @@ endpoint WebContentClient
     did_request_minimize_window() => (Gfx::IntRect window_rect)
     did_request_fullscreen_window() => (Gfx::IntRect window_rect)
     did_request_file(DeprecatedString path, i32 request_id) =|
+    did_request_color_picker(Color current_color) =|
     did_finish_handling_input_event(bool event_was_accepted) =|
 
     did_output_js_console_message(i32 message_index) =|

Userland/Services/WebContent/WebContentServer.ipc

@@ -78,6 +78,7 @@ endpoint WebContentServer
     alert_closed() =|
     confirm_closed(bool accepted) =|
     prompt_closed(Optional<String> response) =|
+    color_picker_closed(Optional<Color> picked_color) =|
 
     toggle_media_play_state() =|
     toggle_media_mute_state() =|