[android] extract RendererBackend from NativeMapView

platform/android/src/android_renderer_backend.cpp

@@ -0,0 +1,55 @@
+#include "android_renderer_backend.hpp"
+
+#include <EGL/egl.h>
+
+#include <cassert>
+
+namespace mbgl {
+namespace android {
+
+/**
+ * From mbgl::View
+ */
+void AndroidRendererBackend::bind() {
+    assert(BackendScope::exists());
+    setFramebufferBinding(0);
+    setViewport(0, 0, getFramebufferSize());
+}
+
+/**
+ * From mbgl::RendererBackend.
+ */
+gl::ProcAddress AndroidRendererBackend::initializeExtension(const char* name) {
+    assert(BackendScope::exists());
+    return eglGetProcAddress(name);
+}
+
+void AndroidRendererBackend::updateViewPort() {
+    assert(BackendScope::exists());
+    setViewport(0, 0, getFramebufferSize());
+}
+
+void AndroidRendererBackend::resizeFramebuffer(int width, int height) {
+    fbWidth = width;
+    fbHeight = height;
+}
+
+PremultipliedImage AndroidRendererBackend::readFramebuffer() const {
+    assert(BackendScope::exists());
+    return RendererBackend::readFramebuffer(getFramebufferSize());
+}
+
+mbgl::Size AndroidRendererBackend::getFramebufferSize() const {
+    return { static_cast<uint32_t>(fbWidth), static_cast<uint32_t>(fbHeight) };
+}
+
+/**
+ * From mbgl::RendererBackend.
+ */
+void AndroidRendererBackend::updateAssumedState() {
+    assumeFramebufferBinding(0);
+    assumeViewport(0, 0, getFramebufferSize());
+}
+
+}
+}