exo: Implement minimal support for version 6 of XDG shell.

components/exo/shell_surface.cc

Index: components/exo/shell_surface.cc
diff --git a/components/exo/shell_surface.cc b/components/exo/shell_surface.cc
index cf8cced1d4c8210fd0d2ee2a0262be8089afd467..97bd44e5a503327ea9b8b9f7e4ce72be58a1cd21 100644
--- a/components/exo/shell_surface.cc
+++ b/components/exo/shell_surface.cc
@@ -637,8 +637,13 @@ void ShellSurface::OnSurfaceCommit() {
   surface_->CheckIfSurfaceHierarchyNeedsCommitToNewSurfaces();
   surface_->CommitSurfaceHierarchy();
 
-  if (enabled() && !widget_)
-    CreateShellSurfaceWidget(ui::SHOW_STATE_NORMAL);
+  if (enabled() && !widget_) {
+    // Defer widget creation until surface contains some contents.
+    if (surface_->content_size().IsEmpty())
+      Configure();
+    else
+      CreateShellSurfaceWidget(ui::SHOW_STATE_NORMAL);
+  }
 
   // Apply the accumulated pending origin offset to reflect acknowledged
   // configure requests.
@@ -1076,8 +1081,6 @@ void ShellSurface::CreateShellSurfaceWidget(ui::WindowShowState show_state) {
 }
 
 void ShellSurface::Configure() {
-  DCHECK(widget_);
-
   // Delay configure callback if |scoped_configure_| is set.
   if (scoped_configure_) {
     scoped_configure_->set_needs_configure();
@@ -1097,10 +1100,16 @@ void ShellSurface::Configure() {
     return;
   }
 
-  uint32_t serial = configure_callback_.Run(
-      widget_->GetWindowBoundsInScreen().size(),
-      ash::wm::GetWindowState(widget_->GetNativeWindow())->GetStateType(),
-      IsResizing(), widget_->IsActive());
+  uint32_t serial;
+  if (widget_) {

[Daniele Castagna, 2016/10/20 20:09:16]

Can you mention in the CL description why the widget_ can now be nullptr?

[reveman, 2017/01/30 22:54:05]

Done.

+    serial = configure_callback_.Run(
+        widget_->GetWindowBoundsInScreen().size(),
+        ash::wm::GetWindowState(widget_->GetNativeWindow())->GetStateType(),
+        IsResizing(), widget_->IsActive());
+  } else {
+    serial = configure_callback_.Run(
+        gfx::Size(), ash::wm::WINDOW_STATE_TYPE_NORMAL, false, false);
+  }
 
   // Apply origin offset and resize component at the first Commit() after this
   // configure request has been acknowledged.