Add support to ngen assets included from nuget package

eng/targets/VisualStudio.targets

@@ -70,11 +70,21 @@
       <_AssetsByPackageId Remove="@(_ExcludedPackageId)" />
     </ItemGroup>
 
+    <!-- Update assets to mark those need to be optimized -->
+    <ItemGroup>
+      <_AssetsByPackageId Update="@(NuGetPackageToIncludeInVsix)">
+        <Optimization Condition="'@(NuGetPackageToIncludeInVsix->'%(Optimization)')' == 'true'">true</Optimization>
+      </_AssetsByPackageId>
+    </ItemGroup>
+
     <!-- Include the assets in the VSIX -->
     <ItemGroup>
       <VSIXCopyLocalReferenceSourceItem Include="@(_AssetsByPackageId->'%(Path)')">
         <ForceIncludeInVsix>true</ForceIncludeInVsix>
         <Private>true</Private>
+        <Ngen Condition="'%(Optimization)' == 'true'">true</Ngen>
+        <NgenArchitecture Condition="'%(Optimization)' == 'true'">All</NgenArchitecture>
+        <NgenPriority Condition="'%(Optimization)' == 'true'">3</NgenPriority>
       </VSIXCopyLocalReferenceSourceItem>
     </ItemGroup>
   </Target>

src/VisualStudio/Setup/Roslyn.VisualStudio.Setup.csproj

@@ -255,7 +255,7 @@
   </ItemGroup>
   <ItemGroup>
     <NuGetPackageToIncludeInVsix Include="Humanizer.Core" />
-    <NuGetPackageToIncludeInVsix Include="Microsoft.CodeAnalysis.FlowAnalysis.Utilities" />
+    <NuGetPackageToIncludeInVsix Include="Microsoft.CodeAnalysis.FlowAnalysis.Utilities" Optimization="true"/>
     <NuGetPackageToIncludeInVsix Include="SQLitePCLRaw.bundle_green" />
     <NuGetPackageToIncludeInVsix Include="Microsoft.CodeAnalysis.Elfie" />
     <!-- Visual Studio ships with some, but not all, of the assemblies in System.Composition, but we need them all -->