Add hooks for changing priorities of warnings to errors in strong mode

pkg/analysis_server/lib/src/protocol_server.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library protocol.server;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/plugin/protocol/protocol_dart.dart';
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart'
@@ skipping 25 matching lines @@
     ErrorProcessor processor = ErrorProcessor.getProcessor(context, error);
     if (processor != null) {
       engine.ErrorSeverity severity = processor.severity;
       // Errors with null severity are filtered out.
       if (severity != null) {
         // Specified severities override.
         serverErrors
             .add(newAnalysisError_fromEngine(lineInfo, error, severity));
       }
     } else {
-      serverErrors.add(newAnalysisError_fromEngine(lineInfo, error));
+      AnalysisError error2 = newAnalysisError_fromEngine(lineInfo, error);
+      bool isStrongMode = context.analysisOptions.strongMode;
+      if (isStrongMode &&
+          error is engine.StaticWarningCode &&
+          (error as engine.StaticWarningCode).isStrongModeError) {
+        error2.severity = AnalysisErrorSeverity.ERROR;
+      }
+      serverErrors.add(error2);
     }
   }
   return serverErrors;
 }
 
 /**
  * Adds [edit] to the [FileEdit] for the given [element].
  */
 void doSourceChange_addElementEdit(
     SourceChange change, engine.Element element, SourceEdit edit) {
@@ skipping 202 matching lines @@
     if (lineInfo != null) {
       engine.LineInfo_Location offsetLocation =
           lineInfo.getLocation(range.offset);
       startLine = offsetLocation.lineNumber;
       startColumn = offsetLocation.columnNumber;
     }
   }
   return new Location(
       source.fullName, range.offset, range.length, startLine, startColumn);
 }