[HDRP] Fix GC allocs (#3136)

* Fix gc alloc errors

* Avoid setting the name of an object during render (gc alloc)

* Avoid gc allocs (for real this time)

Author: pmavridis

com.unity.render-pipelines.high-definition/Runtime/Compositor/AlphaInjection.cs

@@ -27,8 +27,6 @@ public override void Setup()
             var hdrpAsset = HDRenderPipeline.defaultAsset;
             if (hdrpAsset != null)
                 m_Material = CoreUtils.CreateEngineMaterial(hdrpAsset.renderPipelineResources.shaders.alphaInjectionPS);
-
-            name = "AlphaInjection"; // Needed to get a scope name in RenderDoc captures 
         }
 
         public override void Render(CommandBuffer cmd, HDCamera camera, RTHandle source, RTHandle destination)

com.unity.render-pipelines.high-definition/Runtime/Compositor/ChromaKeying.cs

@@ -30,8 +30,6 @@ public override void Setup()
             var hdrpAsset = HDRenderPipeline.defaultAsset;
             if (hdrpAsset != null)
                 m_Material = CoreUtils.CreateEngineMaterial(hdrpAsset.renderPipelineResources.shaders.chromaKeyingPS);
-
-            name = "ChromaKeying"; // Needed to get a scope name in RenderDoc captures 
         }
 
         public override void Render(CommandBuffer cmd, HDCamera camera, RTHandle source, RTHandle destination)

com.unity.render-pipelines.high-definition/Runtime/Compositor/CompositionManager.cs

@@ -551,6 +551,10 @@ void OnDestroy()
                     CoreUtils.Destroy(volume);
                 }
             }
+
+            // We don't need the custom passes anymore
+            var hdPipeline = RenderPipelineManager.currentPipeline as HDRenderPipeline;
+            UnRegisterCustomPasses(hdPipeline);
         }
 
         public void AddInputFilterAtLayer(CompositionFilter filter, int index)
@@ -929,14 +933,12 @@ static internal void RegisterCustomPasses(HDRenderPipeline hdPipeline)
             }
 
             // If custom post processes are not registered in the HDRP asset, they are never executed so we have to add them manually
-            int indx = hdPipeline.asset.beforePostProcessCustomPostProcesses.FindIndex(x => x == typeof(ChromaKeying).AssemblyQualifiedName);
-            if (indx < 0)
+            if (!hdPipeline.asset.beforePostProcessCustomPostProcesses.Contains(typeof(ChromaKeying).AssemblyQualifiedName))
             {
                 hdPipeline.asset.beforePostProcessCustomPostProcesses.Add(typeof(ChromaKeying).AssemblyQualifiedName);
             }
 
-            indx = hdPipeline.asset.beforePostProcessCustomPostProcesses.FindIndex(x => x == typeof(AlphaInjection).AssemblyQualifiedName);
-            if (indx < 0)
+            if (!hdPipeline.asset.beforePostProcessCustomPostProcesses.Contains(typeof(AlphaInjection).AssemblyQualifiedName))
             {
                 hdPipeline.asset.beforePostProcessCustomPostProcesses.Add(typeof(AlphaInjection).AssemblyQualifiedName);
             }
@@ -950,14 +952,12 @@ static internal void UnRegisterCustomPasses(HDRenderPipeline hdPipeline)
                 return;
             }
 
-            int indx = hdPipeline.asset.beforePostProcessCustomPostProcesses.FindIndex(x => x == typeof(ChromaKeying).AssemblyQualifiedName);
-            if (indx >= 0)
+            if (hdPipeline.asset.beforePostProcessCustomPostProcesses.Contains(typeof(ChromaKeying).AssemblyQualifiedName))
             {
                 hdPipeline.asset.beforePostProcessCustomPostProcesses.Remove(typeof(ChromaKeying).AssemblyQualifiedName);
             }
 
-            indx = hdPipeline.asset.beforePostProcessCustomPostProcesses.FindIndex(x => x == typeof(AlphaInjection).AssemblyQualifiedName);
-            if (indx >= 0)
+            if (hdPipeline.asset.beforePostProcessCustomPostProcesses.Contains(typeof(AlphaInjection).AssemblyQualifiedName))
             {
                 hdPipeline.asset.beforePostProcessCustomPostProcesses.Remove(typeof(AlphaInjection).AssemblyQualifiedName);
             }