Don't propagate synchronous Future.wait errors immediately.

sdk/lib/async/future.dart

 // Copyright (c) 2012, 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.
 
 part of dart.async;
 
 /**
  * An object representing a delayed computation.
  *
  * A [Future] is used to represent a potential value, or error,
@@ skipping 304 matching lines @@
         remaining++;
       }
       if (remaining == 0) {
         return new Future.value(const []);
       }
       values = new List/*<T>*/(remaining);
     } catch (e, st) {
       // The error must have been thrown while iterating over the futures
       // list, or while installing a callback handler on the future.
       if (remaining == 0 || eagerError) {
-        // Just complete the error immediately.
-        result._completeError(e, st);
+        // Throw a new Future.error.
+        // Don't just call `result._completeError` since that would propagate
+        // the error too eagerly, not giving the callers time to install
+        // error handlers.
+        // Also, don't use `_asyncCompleteError` since that one doesn't give
+        // zones the chance to intercept the error.
+        return new Future.error(e, st);
       } else {
         // Don't allocate a list for values, thus indicating that there was an
         // error.
         // Set error to the caught exception.
         error = e;
         stackTrace = st;
       }
     }
     return result;
   }
@@ skipping 438 matching lines @@
   if (replacement != null) {
     error = _nonNullError(replacement.error);
     stackTrace = replacement.stackTrace;
   }
   result._completeError(error, stackTrace);
 }
 
 /** Helper function that converts `null` to a [NullThrownError]. */
 Object _nonNullError(Object error) =>
   (error != null) ? error : new NullThrownError();