FrontendCommon: Add a post processing implementation

src/frontend-common/postprocessing_shadergen.h

@@ -0,0 +1,21 @@
+#pragma once
+#include "core/shadergen.h"
+#include "postprocessing_shader.h"
+#include <sstream>
+
+namespace FrontendCommon {
+
+class PostProcessingShaderGen : public ShaderGen
+{
+public:
+  PostProcessingShaderGen(HostDisplay::RenderAPI render_api, bool supports_dual_source_blend);
+  ~PostProcessingShaderGen();
+
+  std::string GeneratePostProcessingVertexShader(const PostProcessingShader& shader);
+  std::string GeneratePostProcessingFragmentShader(const PostProcessingShader& shader);
+
+private:
+  void WriteUniformBuffer(std::stringstream& ss, const PostProcessingShader& shader, bool use_push_constants);
+};
+
+} // namespace FrontendCommon