mus/views: Call to WaitForIncomingMethodCall() can fail.

ui/views/mus/screen_mus.cc

 // Copyright 2016 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/screen_mus.h"
 
 #include "mojo/converters/geometry/geometry_type_converters.h"
 #include "services/shell/public/cpp/connection.h"
 #include "services/shell/public/cpp/connector.h"
 #include "ui/gfx/display_finder.h"
@@ skipping 78 matching lines @@
 
   connector->ConnectToInterface("mojo:mus", &display_manager_);
 
   display_manager_->AddObserver(
       display_manager_observer_binding_.CreateInterfacePtrAndBind());
 
   // We need the set of displays before we can continue. Wait for it.
   //
   // TODO(rockot): Do something better here. This should not have to block tasks
   // from running on the calling thread. http://crbug.com/594852.
-  display_manager_observer_binding_.WaitForIncomingMethodCall();
+  bool success = display_manager_observer_binding_.WaitForIncomingMethodCall();
 
   // The WaitForIncomingMethodCall() should have supplied the set of Displays,
-  // unless mus is going down, in which case encountered_error() is true.
+  // unless mus is going down, in which case encountered_error() is true, or the
+  // call to WaitForIncomingMethodCall() failed.
   if (displays_.empty()) {
-    DCHECK(display_manager_.encountered_error());
+    DCHECK(display_manager_.encountered_error() || !success);

[sky, 2016/04/27 21:09:59]

Isn't encountered_error set in this case?

[sadrul, 2016/04/27 21:39:24]

Apparently not. (it's easy to hit this DCHECK() with
https://codereview.chromium.org/1920033005/ without this patch)

     // In this case we install a default display and assume the process is
     // going to exit shortly so that the real value doesn't matter.
     displays_.push_back(gfx::Display(0xFFFFFFFF, gfx::Rect(0, 0, 801, 802)));
   }
 }
 
 int ScreenMus::FindDisplayIndexById(int64_t id) const {
   for (size_t i = 0; i < displays_.size(); ++i) {
     if (displays_[i].id() == id)
       return static_cast<int>(i);
@@ skipping 131 matching lines @@
   DCHECK_NE(-1, index);
   // Another display must become primary before the existing primary is
   // removed.
   DCHECK_NE(index, primary_display_index_);
   const gfx::Display display = displays_[index];
   FOR_EACH_OBSERVER(gfx::DisplayObserver, observers_,
                     OnDisplayRemoved(display));
 }
 
 }  // namespace views