views/mus: Fix some flaky crashes during test teardown.

ui/views/mus/surface_binding.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/mus/surface_binding.h"
 
 #include <stdint.h>
 
 #include <map>
 #include <utility>
@@ skipping 80 matching lines @@
     (*window_map)[connection] = new PerConnectionState(connector, connection);
     (*window_map)[connection]->Init();
   }
   return (*window_map)[connection];
 }
 
 std::unique_ptr<cc::OutputSurface>
 SurfaceBinding::PerConnectionState::CreateOutputSurface(
     mus::Window* window,
     mus::mojom::SurfaceType surface_type) {
+  if (gpu_.encountered_error())
+    return nullptr;
   // TODO(sky): figure out lifetime here. Do I need to worry about the return
   // value outliving this?
   mus::mojom::CommandBufferPtr cb;
   gpu_->CreateOffscreenGLES2Context(GetProxy(&cb));
 
   scoped_refptr<cc::ContextProvider> context_provider(
       new mus::ContextProvider(cb.PassInterface().PassHandle()));
   return base::WrapUnique(new mus::OutputSurface(
       context_provider, window->RequestSurface(surface_type)));
 }
 
 SurfaceBinding::PerConnectionState::PerConnectionState(
     shell::Connector* connector,
     mus::WindowTreeConnection* connection)
     : connector_(connector), connection_(connection) {}
 
 SurfaceBinding::PerConnectionState::~PerConnectionState() {
   ConnectionToStateMap* window_map = window_states.Pointer()->Get();
   DCHECK(window_map);
   DCHECK_EQ(this, (*window_map)[connection_]);
   window_map->erase(connection_);
   if (window_map->empty()) {
     delete window_map;
     window_states.Pointer()->Set(nullptr);
   }
 }
 
 void SurfaceBinding::PerConnectionState::Init() {
   connector_->ConnectToInterface("mojo:mus", &gpu_);
+
+  // TODO(sad): If connection is lost (e.g. if gpu crashes), then the
+  // connections need to be restored. https://crbug.com/613366
+  // TODO(rockot|yzshen): It is necessary to install a connection-error handler,
+  // even if the handler doesn't actually do anything. https://crbug.com/613371
+  gpu_.set_connection_error_handler([]{});
 }
 
 // SurfaceBinding --------------------------------------------------------------
 
 SurfaceBinding::SurfaceBinding(shell::Connector* connector,
                                mus::Window* window,
                                mus::mojom::SurfaceType surface_type)
     : window_(window),
       surface_type_(surface_type),
       state_(PerConnectionState::Get(connector, window->connection())) {}
 
 SurfaceBinding::~SurfaceBinding() {}
 
 std::unique_ptr<cc::OutputSurface> SurfaceBinding::CreateOutputSurface() {
   return state_->CreateOutputSurface(window_, surface_type_);
 }
 
 }  // namespace views