Re-enable a test that we suspect flaked due to message-loss.

Bug: 816620
Change-Id: I25d8b9d627578946a6c4adb2c220c9401f21c59b
Reviewed-on: https://chromium-review.googlesource.com/959677Reviewed-by: Ken Rockot <rockot@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543386}

ipc/ipc_channel_proxy_unittest.cc

@@ -418,14 +418,11 @@ class IPCChannelBadMessageTest : public IPCChannelMojoTestBase {
   std::unique_ptr<QuitListener> listener_;
 };
 
-#if !defined(OS_WIN)
-  // TODO(jam): for some reason this is flaky on win buildbots.
 TEST_F(IPCChannelBadMessageTest, BadMessage) {
   sender()->Send(new TestMsg_SendBadMessage());
   SendQuitMessageAndWaitForIdle();
   EXPECT_TRUE(DidListenerGetBadMessage());
 }
-#endif
 
 DEFINE_IPC_CHANNEL_MOJO_TEST_CLIENT(ChannelProxyClient) {
   ChannelReflectorListener listener;