Add compile_from_dill test

pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart

Index: pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart b/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
index 3a3a0db071f34e5a9bb39c5fa78c6741fd71c101..ce7bfc08318f459c084cb6f2d533cfdc8fa20d33 100644
--- a/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart
@@ -1026,7 +1026,7 @@ class Emitter extends js_emitter.EmitterBase {
     String libraryName = (!compiler.options.enableMinification ||
             backend.mirrorsData.mustRetainLibraryNames)
         // TODO(johnniwinther): Support library names for entities.
-        ? library is LibraryElement ? library.libraryName : library.name
+        ? library is LibraryElement ? library.libraryName : ''
         : "";
 
     jsAst.Fun metadata =
@@ -1903,7 +1903,12 @@ class Emitter extends js_emitter.EmitterBase {
 
   jsAst.Comment buildGeneratedBy() {
     List<String> options = [];
-    if (compiler.commonElements.mirrorsLibrary != null) options.add('mirrors');
+    if (compiler.commonElements.mirrorsLibrary != null &&
+        !compiler.options.loadFromDill) {
+      // TODO(johnniwinther): Add `isMirrorsUsed` to [BackendData] instead

[Siggi Cherem (dart-lang), 2017/05/30 22:34:42]

+1 - to take this a step further, should we have a notion of a compiler
"configuration" that we serialize here?

Besides csp and mirrors, I'd like to see:
 - the emitter (full/startup)
 - trust flags (trust-types/trust-primitives)
 - optimization levels (disable-inference, no-inlining, and -once we add it-
something like "minimal optimizations")
 - ast vs kernel :)
 

[Johnni Winther, 2017/05/31 09:08:40]

Acknowledged.

+      // of checking `mirrorsLibrary`.
+      options.add('mirrors');
+    }
     if (compiler.options.useContentSecurityPolicy) options.add("CSP");
     return new jsAst.Comment(generatedBy(compiler, flavor: options.join(", ")));
   }