Don't wait unnecessarily.

tests/stub-generator/src/MintMakerPromiseWithStubsTest.dart

Index: tests/stub-generator/src/MintMakerPromiseWithStubsTest.dart
===================================================================
--- tests/stub-generator/src/MintMakerPromiseWithStubsTest.dart	(revision 734)
+++ tests/stub-generator/src/MintMakerPromiseWithStubsTest.dart	(working copy)
@@ -20,7 +20,7 @@
 
   int queryBalance();
   Purse sproutPurse();
-  int deposit(int amount, Purse$Proxy source);
+  Promise<int> deposit(int amount, Purse$Proxy source);
 
 }
 
@@ -57,17 +57,21 @@
     return _mint.createPurse(0);
   }
 
-  int deposit(int amount, Purse$Proxy proxy) {
+  Promise<int> deposit(int amount, Purse$Proxy proxy) {
     if (amount < 0) throw "Ha ha";
     // Because we are in the same isolate as the other purse, we can
     // retrieve the proxy's local PurseImpl object and act on it
     // directly. Further, a forged purse will not be convertible, and
     // so an attempt to use it will fail.
-    PurseImpl source = proxy.dynamic.local;
-    if (source._balance < amount) throw "Not enough dough.";
-    _balance += amount;
-    source._balance -= amount;
-    return _balance;
+    Promise<int> balance = new Promise<int>();
+    proxy.addCompleteHandler((_) {
+      PurseImpl source = proxy.dynamic.local;
+      if (source._balance < amount) throw "Not enough dough.";
+      _balance += amount;
+      source._balance -= amount;
+      balance.complete(_balance);
+    });
+    return balance;
   }
 
   Mint _mint;