[HDRP] Fix decal draw order for ShaderGraph decal materials (#3018)

* Fixed ShaderGraph decal draw order

* Updated changelog

Co-authored-by: sebastienlagarde <sebastien@unity3d.com>

Author: alelievr

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -36,6 +36,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed an issue with the frame count management for the volumetric fog (case 1299251).
 - Fixed issue with shadow mask and area lights.
 - Fixed an issue with the capture callback (now includes post processing results).
+- Fixed decal draw order for ShaderGraph decal materials.
 
 ### Changed
 - Removed the material pass probe volumes evaluation mode.

com.unity.render-pipelines.high-definition/Runtime/Material/Decal/DecalSystem.cs

@@ -859,9 +859,9 @@ public int DrawOrder
             {
                 get
                 {
-                    if (m_IsHDRenderPipelineDecal)
+                    if (this.m_Material.HasProperty(HDShaderIDs._DrawOrder))
                     {
-                        return this.m_Material.GetInt("_DrawOrder");
+                        return this.m_Material.GetInt(HDShaderIDs._DrawOrder);
                     }
                     else
                     {

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDStringConstants.cs

@@ -243,6 +243,7 @@ static class HDShaderIDs
         public static readonly int _DecalNormalBufferStencilRef = Shader.PropertyToID("_DecalNormalBufferStencilRef");
         public static readonly int _DecalPrepassTexture = Shader.PropertyToID("_DecalPrepassTexture");
         public static readonly int _DecalPrepassTextureMS = Shader.PropertyToID("_DecalPrepassTextureMS");
+        public static readonly int _DrawOrder = Shader.PropertyToID("_DrawOrder");
 
 
         public static readonly int _WorldSpaceCameraPos = Shader.PropertyToID("_WorldSpaceCameraPos");