Use RenderTextureDesc to create VR RTs

We can now fetch RenderTextureDesc for VR eye textures from VRDevice.  This greatly simplifies the creation process for VR RTs.

We should also do this for the camera 'back buffer'.

Assets/LowEndMobilePipeline/LowEndMobilePipeline.cs

 
                 if (VRSettings.isDeviceActive)
                 {
-                    int w = VRSettings.eyeTextureWidth;
-                    int h = VRSettings.eyeTextureHeight;
-
-                    var aa = QualitySettings.antiAliasing;
-                    if (aa < 1)
-                        aa = 1;
-
-
-                    // TODO: this won't work in...the Player
-                    var stereoPath = PlayerSettings.stereoRenderingPath;
-                    if (StereoRenderingPath.Instancing == stereoPath) // can't actually check for GetGraphicsCaps().hasRenderTargetArrayIndexFromAnyShader...yet
-                    {
-                        bindTempRTCmd.GetTemporaryRTArray(intermediateRT, w, h, 2, 0, FilterMode.Point, RenderTextureFormat.Default, RenderTextureReadWrite.Default, aa, true);
-                        bindTempRTCmd.GetTemporaryRTArray(intermediateDepthRT, w, h, 2, 24, FilterMode.Point, RenderTextureFormat.Depth);
-                    }
-                    else
-                    {
-                        bindTempRTCmd.GetTemporaryRT(intermediateRT, w, h, 0, FilterMode.Point, RenderTextureFormat.Default, RenderTextureReadWrite.Default, aa, true);
-                        bindTempRTCmd.GetTemporaryRT(intermediateDepthRT, w, h, 24, FilterMode.Point, RenderTextureFormat.Depth);
-                    }
-
-                    bindTempRTCmd.SetRenderTarget(intermediateRTID, intermediateDepthRTID);
+                    RenderTextureDesc vrDesc = VRDevice.GetVREyeTextureDesc();
+                    vrDesc.depthBufferBits = 24;
+                    bindTempRTCmd.GetTemporaryRT(intermediateRT, vrDesc, FilterMode.Point);
+                    bindTempRTCmd.SetRenderTarget(intermediateRTID);
+                   
                     context.ExecuteCommandBuffer(bindTempRTCmd);
                     bindTempRTCmd.Dispose();
                 }
                     // this does the combined color/depth RT
                     bindTempRTCmd.GetTemporaryRT(intermediateRT, w, h, 24, FilterMode.Point, RenderTextureFormat.Default, RenderTextureReadWrite.Default, aa, true);
                     bindTempRTCmd.SetRenderTarget(intermediateRTID);
-                    //bindTempRTCmd.GetTemporaryRT(intermediateDepthRT, w, h, 24, FilterMode.Point, RenderTextureFormat.Depth);
-                    //bindTempRTCmd.SetRenderTarget(intermediateRTID, intermediateDepthRTID);
                     context.ExecuteCommandBuffer(bindTempRTCmd);
                     bindTempRTCmd.Dispose();
                 }