Fix shadows for tessellation

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.shader

 
     #pragma target 4.5
     #pragma only_renderers d3d11 ps4 metal // TEMP: until we go futher in dev
-    //#pragma enable_d3d11_debug_symbols
+    // #pragma enable_d3d11_debug_symbols
 
     //-------------------------------------------------------------------------------------
     // Variant

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitTessellation.hlsl

     // TODO: Handle inverse culling (for mirror)!
     if (_TessellationBackFaceCullEpsilon > -0.99) // Is backface culling enabled ?
     {
-        faceCull = BackFaceCullTriangle(p0, p1, p2, _TessellationBackFaceCullEpsilon, _WorldSpaceCameraPos);
+        faceCull = BackFaceCullTriangle(p0, p1, p2, _TessellationBackFaceCullEpsilon, GetCurrentCameraPosition());
     }
 #endif
 
     // Distance based tessellation
     if (_TessellationFactorMaxDistance > 0.0)
     {
-        float3 distFactor = GetDistanceBasedTessFactor(p0, p1, p2, _WorldSpaceCameraPos, _TessellationFactorMinDistance, _TessellationFactorMaxDistance);
+        float3 distFactor = GetDistanceBasedTessFactor(p0, p1, p2, GetCurrentCameraPosition(), _TessellationFactorMinDistance, _TessellationFactorMaxDistance);
         // We square the disance factor as it allow a better percptual descrease of vertex density.
         tessFactor *= distFactor * distFactor;
     }

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitTessellation.shader

 
     #pragma target 5.0
     #pragma only_renderers d3d11 ps4// TEMP: until we go futher in dev
+    // #pragma enable_d3d11_debug_symbols
 
     //-------------------------------------------------------------------------------------
     // Variant

Assets/ScriptableRenderPipeline/HDRenderPipeline/ShaderVariables.hlsl

     return mul(GetWorldToHClipMatrix(), float4(positionWS, 1.0));
 }
 
+float3 GetCurrentCameraPosition()
+{
+#if SHADERPASS != SHADERPASS_DEPTH_ONLY
+    return _WorldSpaceCameraPos;
+#else
+    // TEMP: this is a workaround until the shadow map pass sets '_WorldSpaceCameraPos'.
+    // This code is far more expensive than loading a constant from a cbuffer!
+    float4x4 viewMat   = transpose(GetWorldToViewMatrix());
+    float3   rotCamPos = viewMat[3].xyz;
+   return mul((float3x3)viewMat, -rotCamPos);
+#endif
+}
+
-    float3 V = _WorldSpaceCameraPos.xyz - positionWS;
+    float3 V = GetCurrentCameraPosition() - positionWS;
 
     // Uncomment this once the compiler bug is fixed.
     // if (unity_OrthoParams.w == 1.0)