Makes ApplicationRunner delete the delegate before the app

To do otherwise means the delegate outlives the app, which is error
prone (I was hitting an asan error running apptests). Before this
patch the destruction order was:
1. app
2. messageloop
3. delegate

Between 2 and 3 we may pump events posted by the delegate, which is
problematic since the app has been deleted.

Now it's:
. delegate
. app
. messageloop

BUG=none
TEST=none
R=ben@chromium.org

Review URL: https://codereview.chromium.org/1160643003

Cr-Commit-Position: refs/heads/master@{#331877}

1 files changed, 4 insertions, 1 deletions

diff --git a/mojo/application/public/cpp/lib/application_runner.cc b/mojo/application/public/cpp/lib/application_runner.cc
index cc32b9f..8ed7482 100644
--- a/mojo/application/public/cpp/lib/application_runner.cc
+++ b/mojo/application/public/cpp/lib/application_runner.cc
@@ -67,8 +67,11 @@ MojoResult ApplicationRunner::Run(MojoHandle application_request_handle) {
                          MakeRequest<Application>(MakeScopedHandle(
                              MessagePipeHandle(application_request_handle))));
     loop->Run();
+    // It's very common for the delegate to cache the app and terminate on
+    // errors. If we don't delete the delegate before the app we run the risk
+    // of the delegate having a stale reference to the app and trying to use it.
+    delegate_.reset();
   }
-  delegate_.reset();
   return MOJO_RESULT_OK;
 }