Refactor SSAO apply

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/Core.hlsl

     ApplyFogColor(color, unity_FogColor.rgb, fogFactor);
 }
 
-void ApplySSAO(inout half3 occlusion, float4 texcoord)
+half3 SSAO(float4 texcoord)
-    
-    //TODO: The occlusion term is only a half, breaking colored AO.
-    //TODO: Find better occlusion mix method.
-    occlusion *= lerp(_AmbientOcclusionParam.rgb, float3(1.0, 1.0, 1.0), ssao); 
+    return lerp(_AmbientOcclusionParam.rgb, float3(1.0, 1.0, 1.0), ssao); 
 }
 
 // Stereo-related bits

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/LightweightPassLit.hlsl

 
     SurfaceData surfaceData;
     InitializeStandardLitSurfaceData(IN.uv, surfaceData);
-    ApplySSAO(surfaceData.occlusion, IN.shadowCoord); //The shadowcoord is the screen space position.
 
     InputData inputData;
     InitializeInputData(IN, surfaceData.normalTS, inputData);
     ApplyFog(color.rgb, inputData.fogCoord);
-    return color;
+    return half4(color.rgb * SSAO(IN.shadowCoord), color.a);
 }
 
 // Used for Standard shader
 #elif defined(_DEBUG_SMOOTHNESS)
     debug = surfaceData.smoothness;
 #elif defined(_DEBUG_OCCLUSION)
-    ApplySSAO(surfaceData.occlusion, IN.shadowCoord);
-    debug = surfaceData.occlusion;
+    debug = surfaceData.occlusion * SSAO(IN.shadowCoord);
 #elif defined(_DEBUG_SHADOWS)
     debug = RealtimeShadowAttenuation(IN.shadowCoord);
 #endif

ScriptableRenderPipeline/LightweightPipeline/LWRP/Shaders/Subsurface/LightweightPassLit.hlsl

 
     SurfaceData surfaceData;
     InitializeStandardLitSurfaceData(IN.uv, surfaceData);
-    ApplySSAO(surfaceData.occlusion, IN.shadowCoord);
 
     InputData inputData;
     InitializeInputData(IN, surfaceData.normalTS, inputData);
     half4 color = LightweightFragmentPBR(inputData, surfaceData.albedo, surfaceData.metallic, surfaceData.specular, surfaceData.smoothness, surfaceData.occlusion, surfaceData.emission, surfaceData.alpha, curvature);
 
     ApplyFog(color.rgb, inputData.fogCoord);
-    return color;
+    return half4(color.rgb * SSAO(IN.shadowCoord), color.a);
 }
 
 // Used for Standard shader