Ladybird/Android: Move JNI functions into their own files

This should be easier to work on, and keeps the layers of the native
code nice and clean cut.

Ladybird/Android/src/main/cpp/WebViewImplementationNative.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Userland/Libraries/LibWebView/ViewImplementation.h>
+#include <android/bitmap.h>
+#include <jni.h>
+
+namespace Ladybird {
+class WebViewImplementationNative : public WebView::ViewImplementation {
+public:
+    WebViewImplementationNative(jobject thiz);
+
+    virtual Gfx::IntRect viewport_rect() const override { return m_viewport_rect; }
+    virtual Gfx::IntPoint to_content_position(Gfx::IntPoint p) const override { return p; }
+    virtual Gfx::IntPoint to_widget_position(Gfx::IntPoint p) const override { return p; }
+    virtual void update_zoom() override { }
+
+    NonnullRefPtr<WebView::WebContentClient> bind_web_content_client();
+
+    virtual void create_client(WebView::EnableCallgrindProfiling) override;
+
+    void paint_into_bitmap(void* android_bitmap_raw, AndroidBitmapInfo const& info);
+
+    void set_viewport_geometry(int w, int h);
+    void set_device_pixel_ratio(float f);
+
+    static jclass global_class_reference;
+    static jmethodID bind_webcontent_method;
+    static jmethodID invalidate_layout_method;
+    static JavaVM* global_vm;
+
+    jobject java_instance() const { return m_java_instance; }
+
+private:
+    jobject m_java_instance = nullptr;
+    Gfx::IntRect m_viewport_rect;
+};
+}