Add an http_throttle package.

sdk/lib/_internal/pub/lib/src/log.dart

Index: sdk/lib/_internal/pub/lib/src/log.dart
diff --git a/sdk/lib/_internal/pub/lib/src/log.dart b/sdk/lib/_internal/pub/lib/src/log.dart
index 6821581033d95c23e2838f1c385acf8cea37dfe3..3eb25573c89c4fb50a0b7582e43f5c12aff10ae6 100644
--- a/sdk/lib/_internal/pub/lib/src/log.dart
+++ b/sdk/lib/_internal/pub/lib/src/log.dart
@@ -11,6 +11,7 @@ import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:source_maps/source_maps.dart';
+import 'package:source_span/source_span.dart';
 import 'package:stack_trace/stack_trace.dart';
 
 import 'exceptions.dart';
@@ -317,6 +318,8 @@ void exception(exception, [StackTrace trace]) {
   // spew a stack trace on our users.
   if (exception is SpanException) {
     error(exception.toString(useColors: canUseSpecialChars));
+  } else if (exception is SourceSpanException) {
+    error(exception.toString(color: canUseSpecialChars));
   } else {
     error(getErrorMessage(exception));
   }
@@ -507,7 +510,8 @@ class _JsonLogger {
     }
 
     // If the error came from a file, include the path.
-    if (error is SpanException && error.span.sourceUrl != null) {
+    if ((error is SpanException || error is SourceSpanException) &&
+        error.span.sourceUrl != null) {
       errorJson["path"] = p.fromUri(error.span.sourceUrl);
     }