Support optional package name arguments to --show-package-warnings

pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart

Index: pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
diff --git a/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart b/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
index e4bd449879dcf2c9e8dd53742a69d5b56e3a435c..6a156ae42566f1f634b35ababa5782ab5350c026 100644
--- a/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
+++ b/pkg/compiler/lib/src/diagnostics/diagnostic_listener.dart
@@ -16,8 +16,10 @@ class DiagnosticOptions {
   /// Emit terse diagnostics without howToFix.
   final bool terseDiagnostics;
 
-  /// If `true`, warnings and hints not from user code are reported.
-  final bool showPackageWarnings;
+  /// List of packages for which warnings and hints are reported. If `null`,
+  /// no package warnings or hints are reported. If empty, all warnings and
+  /// hints are reported.
+  final List<String> _shownPackageWarnings;
 
   /// If `true`, warnings are not reported.
   final bool suppressWarnings;
@@ -33,7 +35,29 @@ class DiagnosticOptions {
     this.fatalWarnings: false,
     this.suppressHints: false,
     this.terseDiagnostics: false,
-    this.showPackageWarnings: false});
+    List<String> shownPackageWarnings: null})
+      : _shownPackageWarnings = shownPackageWarnings;
+
+
+  /// Returns `true` if warnings and hints are shown for all packages.
+  bool get showAllPackageWarnings {
+    return _shownPackageWarnings != null && _shownPackageWarnings.isEmpty;
+  }
+
+  /// Returns `true` if warnings and hints are hidden for all packages.
+  bool get hidePackageWarnings => _shownPackageWarnings == null;
+
+  /// Returns `true` if warnings should be should for [uri].
+  bool showPackageWarningsFor(Uri uri) {
+    if (showAllPackageWarnings) {
+      return true;
+    }
+    if (_shownPackageWarnings != null) {
+      return uri.scheme == 'package' &&
+          _shownPackageWarnings.contains(uri.pathSegments.first);
+    }
+    return false;
+  }
 }
 
 // TODO(johnniwinther): Rename and cleanup this interface. Add severity enum.