More uses of the new try-catch syntax.

pkg/dartdoc/dartdoc.dart

Index: pkg/dartdoc/dartdoc.dart
diff --git a/pkg/dartdoc/dartdoc.dart b/pkg/dartdoc/dartdoc.dart
index 075e15d108d5cbdef80b473acd27ef99b742d530..c2a0db1bccd6d54b455cecbaab1fb697bcc00771 100644
--- a/pkg/dartdoc/dartdoc.dart
+++ b/pkg/dartdoc/dartdoc.dart
@@ -253,7 +253,7 @@ void cleanOutputDirectory(Path path) {
     // due to invalid result from dir.existsSync() (probably due to race
     // conditions).
     outputDir.createSync();
-  } catch (DirectoryIOException e) {
+  } on DirectoryIOException catch (e) {
     // Ignore.
   }
 }
@@ -520,7 +520,7 @@ class Dartdoc {
       // race conditions).
       try {
         dir.createSync();
-      } catch (DirectoryIOException e) {
+      } on DirectoryIOException catch (e) {
         // Ignore.
       }
     }
@@ -696,7 +696,7 @@ class Dartdoc {
       // race conditions).
       try {
         dir.createSync();
-      } catch (DirectoryIOException e) {
+      } on DirectoryIOException catch (e) {
         // Ignore.
       }
     }