LibWeb: Implement CanvasRenderingContext2D.save()

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp

@@ -313,4 +313,11 @@ void CanvasRenderingContext2D::put_image_data(const ImageData& image_data, float
     did_draw(Gfx::FloatRect(x, y, image_data.width(), image_data.height()));
 }
 
+// https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-save
+void CanvasRenderingContext2D::save()
+{
+    // The save() method steps are to push a copy of the current drawing state onto the drawing state stack.
+    m_drawing_state_stack.append(m_drawing_state);
+}
+
 }

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h

@@ -69,6 +69,8 @@ public:
     RefPtr<ImageData> create_image_data(int width, int height) const;
     void put_image_data(const ImageData&, float x, float y);
 
+    void save();
+
     HTMLCanvasElement* canvas() { return m_element; }
 
 private:
@@ -89,6 +91,7 @@ private:
     };
 
     DrawingState m_drawing_state;
+    Vector<DrawingState> m_drawing_state_stack;
 
     Gfx::Path m_path;
 };

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl

@@ -31,6 +31,8 @@ interface CanvasRenderingContext2D {
     ImageData createImageData(double sw, double sh);
     undefined putImageData(ImageData imagedata, double dx, double dy);
 
+    undefined save();
+
     readonly attribute HTMLCanvasElement canvas;
 
 };