fix framework assembly resolution for net35 (#2557)

TestAssets/TestProjects/TestLibraryWithMultipleFrameworks/Program.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Xml;
 
 namespace ConsoleApplication
 {
@@ -7,6 +8,10 @@ namespace ConsoleApplication
         public static void Main()
         {
             Console.WriteLine("Hello World!");
+#if NET20 || NET35 || NET45 || NET461
+            // Force XmlDocument to be used
+            var doc = new XmlDocument();
+#endif
         }
     }
 }

TestAssets/TestProjects/TestLibraryWithMultipleFrameworks/project.json

@@ -5,11 +5,28 @@
   },
   "dependencies": {},
   "frameworks": {
-    "net20": {},
-    "net35": {},
-    "net40": {},
-    "net461": {},
+    "net20": {
+        "frameworkAssemblies": {
+            "System.Xml": {}
+        }
+    },
+    "net35": {
+        "frameworkAssemblies": {
+            "System.Xml": {}
+        }
+    },
+    "net40": {
+        "frameworkAssemblies": {
+            "System.Xml": {}
+        }
+    },
+    "net461": {
+        "frameworkAssemblies": {
+            "System.Xml": {}
+        }
+    },
     "netstandard1.5": {
+      "imports": "dnxcore50",
       "dependencies": {
         "NETStandard.Library": "1.5.0-rc2-24018"
       }

src/Microsoft.DotNet.ProjectModel/Resolution/FrameworkReferenceResolver.cs

@@ -210,7 +210,7 @@ namespace Microsoft.DotNet.ProjectModel.Resolution
             // Check for legacy frameworks
             if (PlatformServices.Default.Runtime.OperatingSystemPlatform == Platform.Windows &&
                 targetFramework.IsDesktop() &&
-                targetFramework.Version <= new Version(3, 5))
+                targetFramework.Version <= new Version(3, 5, 0, 0))
             {
                 return GetLegacyFrameworkInformation(targetFramework, referenceAssembliesPath);
             }