Enable Hot Reload on Windows (backed by gen_snapshot) (#8512)

* Enable Hot Reload on Windows (backed by gen_snapshot)

\o/

Two caveats:
* Hot Reload on Windows is slower than on other platforms because gen_snapshot is slower then sky_snapshot
* We currently cannot hot reload projects with spaces in the path

* enable tests
diff --git a/packages/flutter_tools/lib/src/build_info.dart b/packages/flutter_tools/lib/src/build_info.dart
index 2b3e697..5facec6 100644
--- a/packages/flutter_tools/lib/src/build_info.dart
+++ b/packages/flutter_tools/lib/src/build_info.dart
@@ -66,7 +66,8 @@
   android_x86,
   ios,
   darwin_x64,
-  linux_x64
+  linux_x64,
+  windows_x64
 }
 
 String getNameForTargetPlatform(TargetPlatform platform) {
@@ -83,6 +84,8 @@
       return 'darwin-x64';
     case TargetPlatform.linux_x64:
       return 'linux-x64';
+    case TargetPlatform.windows_x64:
+      return 'windows-x64';
   }
   assert(false);
   return null;