Make Analyzer, VM and dart2js accept URI strings as part-of library identifier.

pkg/analyzer/lib/src/task/dart.dart

Index: pkg/analyzer/lib/src/task/dart.dart
diff --git a/pkg/analyzer/lib/src/task/dart.dart b/pkg/analyzer/lib/src/task/dart.dart
index 05528d7f03960538894c15a1bc7dd2c17eab31bf..b01c85fad665d961149c147be013a93356639a7b 100644
--- a/pkg/analyzer/lib/src/task/dart.dart
+++ b/pkg/analyzer/lib/src/task/dart.dart
@@ -1618,7 +1618,8 @@ class BuildLibraryElementTask extends SourceBasedAnalysisTask {
         }
       }
     }
-    if (hasPartDirective && libraryNameNode == null) {
+    if (hasPartDirective && libraryNameNode == null &&
+        !context.analysisOptions.enableUriInPartOf) {

[Brian Wilkerson, 2017/01/25 17:05:14]

Will we issue a warning if a part file contains a part-of directive that uses a
library name when the library doesn't have a name? (I'm assuming that's still an
error.)

[Lasse Reichstein Nielsen, 2017/01/26 10:39:13]

It's still a warning, and I don't think there is a warning in that case.
I didn't find the place to change for that (I'm assuming there is a warning
somewhere if the names don't match, and this should just be the same thing - the
non-empty part-of name doesn't match the empty library name).

       AnalysisError error;
       if (partsLibraryName != _UNKNOWN_LIBRARY_NAME &&
           partsLibraryName != null) {