Grpc.Core managed project now depends on native nuget packages with openssl and zlib

src/csharp/Grpc.Core/Grpc.Core.csproj

 <?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.props" Condition="Exists('..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.props')" />
+  <Import Project="..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.props" Condition="Exists('..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.props')" />
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
@@ -10,6 +12,7 @@
     <RootNamespace>Grpc.Core</RootNamespace>
     <AssemblyName>Grpc.Core</AssemblyName>
     <TargetFrameworkVersion>v4.5</TargetFrameworkVersion>
+    <NuGetPackageImportStamp>8bb563fb</NuGetPackageImportStamp>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -100,7 +103,16 @@
     <Otherwise />
   </Choose>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
-  <ItemGroup>
-    <Folder Include="Stub\" />
-  </ItemGroup>
+  <ItemGroup />
+  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
+    <PropertyGroup>
+      <ErrorText>This project references NuGet package(s) that are missing on this computer. Enable NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
+    </PropertyGroup>
+    <Error Condition="!Exists('..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.props'))" />
+    <Error Condition="!Exists('..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.targets'))" />
+    <Error Condition="!Exists('..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.props')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.props'))" />
+    <Error Condition="!Exists('..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.targets'))" />
+  </Target>
+  <Import Project="..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.targets" Condition="Exists('..\packages\grpc.dependencies.openssl.redist.1.0.2.2\build\portable-net45\grpc.dependencies.openssl.redist.targets')" />
+  <Import Project="..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.targets" Condition="Exists('..\packages\grpc.dependencies.zlib.redist.1.2.8.9\build\portable-net45\grpc.dependencies.zlib.redist.targets')" />
 </Project>
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src/csharp/Grpc.Core/packages.config

 <?xml version="1.0" encoding="utf-8"?>
 <packages>
+  <package id="grpc.dependencies.openssl.redist" version="1.0.2.2" targetFramework="net45" />
+  <package id="grpc.dependencies.zlib.redist" version="1.2.8.9" targetFramework="net45" />
   <package id="System.Collections.Immutable" version="1.1.34-rc" targetFramework="net45" />
 </packages>
\ No newline at end of file