aura: Try to make Linux host resize code more reliable.

ui/aura/desktop_host_linux.cc

Index: ui/aura/desktop_host_linux.cc
diff --git a/ui/aura/desktop_host_linux.cc b/ui/aura/desktop_host_linux.cc
index ed47ca21dad976628412990014f2c581be1e0b07..a90dc67a538ddf93c2153d09f3c410ab8f862922 100644
--- a/ui/aura/desktop_host_linux.cc
+++ b/ui/aura/desktop_host_linux.cc
@@ -377,14 +377,24 @@ gfx::AcceleratedWidget DesktopHostLinux::GetAcceleratedWidget() {
 void DesktopHostLinux::Show() {
   XMapWindow(xdisplay_, xwindow_);
 
+  // Wait for notification that the window is mapped, which happens
+  // asynchronously if there's a window manager running.  Ideally we wouldn't
+  // need to wait for this, but some window managers don't do anything to let us
+  // know that they're there (*cough*ion3*cough*), in which case we need to make
+  // sure that the window is mapped before sending a SetInputFocus request.
+  while (true) {
+    XEvent event;
+    XWindowEvent(xdisplay_, xwindow_, StructureNotifyMask, &event);
+    if (event.type == MapNotify)
+      break;
+  }
+
   // If there's no window manager running, we need to assign the X input focus
-  // to our host window.  (If there's no window manager running, it should also
-  // be safe to assume that the host window will have been mapped by the time
-  // that our SetInputFocus request is received.)
-  if (!IsWindowManagerPresent())
+  // to our host window.
+  if (!IsWindowManagerPresent()) {
     XSetInputFocus(xdisplay_, xwindow_, RevertToNone, CurrentTime);
-
-  XFlush(xdisplay_);
+    XFlush(xdisplay_);
+  }
 }
 
 gfx::Size DesktopHostLinux::GetSize() const {