Fixed MettalicGloss map not being applied.

ScriptableRenderPipeline/LightweightPipeline/Editor/ShaderGUI/LightweightStandardShaderGUI.cs

 using System;
+using UnityEditor.Experimental.Rendering.LightweightPipeline;
 using UnityEngine;
 
 namespace UnityEditor
         {
             // Note: keywords must be based on Material value not on MaterialProperty due to multi-edit & material animation
             // (MaterialProperty value might come from renderer material property block)
-            SetKeyword(material, "_NORMALMAP", material.GetTexture("_BumpMap") || material.GetTexture("_DetailNormalMap"));
+            LightweightShaderHelper.SetKeyword(material, "_NORMALMAP", material.GetTexture("_BumpMap") || material.GetTexture("_DetailNormalMap"));
-            SetKeyword(material, "_SPECULAR_SETUP", workflowMode == WorkflowMode.Specular);
-            SetKeyword(material, "_METALLIC_SETUP", workflowMode == WorkflowMode.Metallic);
-            SetKeyword(material, "_PARALLAXMAP", material.GetTexture("_ParallaxMap"));
-            SetKeyword(material, "_DETAIL_MULX2", material.GetTexture("_DetailAlbedoMap") || material.GetTexture("_DetailNormalMap"));
+            LightweightShaderHelper.SetKeyword(material, "_SPECULAR_SETUP", workflowMode == WorkflowMode.Specular);
+            LightweightShaderHelper.SetKeyword(material, "_METALLIC_SETUP", workflowMode == WorkflowMode.Metallic);
+            LightweightShaderHelper.SetKeyword(material, "_METALLICSPECGLOSSMAP", material.GetTexture("_MetallicSpecGlossMap") != null);
+            LightweightShaderHelper.SetKeyword(material, "_PARALLAXMAP", material.GetTexture("_ParallaxMap"));
+            LightweightShaderHelper.SetKeyword(material, "_DETAIL_MULX2", material.GetTexture("_DetailAlbedoMap") || material.GetTexture("_DetailNormalMap"));
 
             // A material's GI flag internally keeps track of whether emission is enabled at all, it's enabled but has no effect
             // or is enabled and may be modified at runtime. This state depends on the values of the current flag and emissive color.
-            SetKeyword(material, "_EMISSION", shouldEmissionBeEnabled);
+            LightweightShaderHelper.SetKeyword(material, "_EMISSION", shouldEmissionBeEnabled);
-                SetKeyword(material, "_SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A", GetSmoothnessMapChannel(material) == SmoothnessMapChannel.AlbedoAlpha);
+                LightweightShaderHelper.SetKeyword(material, "_SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A", GetSmoothnessMapChannel(material) == SmoothnessMapChannel.AlbedoAlpha);
+            material.shaderKeywords = null;
-
-        static void SetKeyword(Material m, string keyword, bool state)
-        {
-            if (state)
-                m.EnableKeyword(keyword);
-            else
-                m.DisableKeyword(keyword);
-        }
-} // namespace UnityEditor
+}

Tests/GraphicsTests/RenderPipeline/LightweightPipeline/Scenes/024_Shader_PBRvalidation/PBRtest.mat

   m_PrefabInternal: {fileID: 0}
   m_Name: PBRtest
   m_Shader: {fileID: 4800000, guid: 933532a4fcc9baf4fa0491de14d08ed7, type: 3}
-  m_ShaderKeywords: _METALLICGLOSSMAP _METALLIC_SETUP
+  m_ShaderKeywords: _METALLICSPECGLOSSMAP _METALLIC_SETUP
   m_LightmapFlags: 4
   m_EnableInstancingVariants: 0
   m_DoubleSidedGI: 0