Add missing message-received expectation to IPCMojoBootstrapTest.

Some of these tests expected a message from the child process, and would
verify that it was valid/invalid as expected, but would still pass if
no message were received at all.

Bug: 816620
Change-Id: Ie8acf85086f4416c7023118673c40d00a2e190d7
Reviewed-on: https://chromium-review.googlesource.com/955554Reviewed-by: Ken Rockot <rockot@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542296}

ipc/ipc_mojo_bootstrap_unittest.cc

@@ -65,7 +65,11 @@ class PeerPidReceiver : public IPC::mojom::Channel {
       : binding_(this, std::move(request)),
         on_peer_pid_set_(on_peer_pid_set),
         message_expectation_(message_expectation) {}
-  ~PeerPidReceiver() override {}
+  ~PeerPidReceiver() override {
+    bool expected_message =
+        message_expectation_ != MessageExpectation::kNotExpected;
+    EXPECT_EQ(expected_message, received_message_);
+  }
 
   // mojom::Channel:
   void SetPeerPid(int32_t pid) override {
@@ -77,6 +81,7 @@ class PeerPidReceiver : public IPC::mojom::Channel {
                base::Optional<std::vector<mojo::native::SerializedHandlePtr>>
                    handles) override {
     ASSERT_NE(MessageExpectation::kNotExpected, message_expectation_);
+    received_message_ = true;
 
     IPC::Message message(reinterpret_cast<const char*>(data.data()),
                          static_cast<uint32_t>(data.size()));
@@ -97,6 +102,8 @@ class PeerPidReceiver : public IPC::mojom::Channel {
   MessageExpectation message_expectation_;
   int32_t peer_pid_ = -1;
 
+  bool received_message_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(PeerPidReceiver);
 };