add --x-package-warnings-prefix option to dartanalyzer

pkg/analyzer_cli/lib/src/error_formatter.dart

Index: pkg/analyzer_cli/lib/src/error_formatter.dart
diff --git a/pkg/analyzer_cli/lib/src/error_formatter.dart b/pkg/analyzer_cli/lib/src/error_formatter.dart
index 0154d739978d78ad0672cfdbb29af0c6c81b6ca8..9d9ea687b1e45633838867b7958cf8b335b3db7a 100644
--- a/pkg/analyzer_cli/lib/src/error_formatter.dart
+++ b/pkg/analyzer_cli/lib/src/error_formatter.dart
@@ -21,6 +21,10 @@ typedef ProcessedSeverity _SeverityProcessor(AnalysisError error);
 /// The two format options are a user consumable format and a machine consumable
 /// format.
 class ErrorFormatter {
+  /// The total number of errors sent to [formatErrors].
+  static int get inputErrorCount => _inputErrorCount;
+  static int _inputErrorCount = 0;

[Brian Wilkerson, 2016/03/18 14:13:17]

This looks like it's duplicating some work that Phil recently did (and might not
be committed yet. You should coordinate with him on it.

[skybrian, 2016/03/18 22:32:44]

It's a slightly different statistic. Merged into AnalysisStats.

+
   final StringSink out;
   final CommandLineOptions options;
   final _SeverityProcessor processSeverity;
@@ -83,6 +87,8 @@ class ErrorFormatter {
   }
 
   void formatErrors(List<AnalysisErrorInfo> errorInfos) {
+    _inputErrorCount += errorInfos.length;
+
     var errors = new List<AnalysisError>();
     var errorToLine = new Map<AnalysisError, LineInfo>();
     for (AnalysisErrorInfo errorInfo in errorInfos) {