[MR UI] Set dialog width in MediaRouterDialogDelegate::GetDialogSize() if not set

chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.cc

Index: chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.cc
diff --git a/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.cc b/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.cc
index de13d04f3e1011061e939c5d3ee6603d15308930..c56f32f20ed22a45d199f42fc9d52e3ae3225fbd 100644
--- a/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.cc
+++ b/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.cc
@@ -79,6 +79,10 @@ class MediaRouterDialogDelegate : public WebDialogDelegate {
 
   void GetDialogSize(gfx::Size* size) const override {
     DCHECK(size);
+    // We set the dialog width if it's not set, so that the dialog is
+    // center-aligned horizontally when it appears.
+    if (size->width() != kWidth)
+      size->set_width(kWidth);
     // GetDialogSize() is called when the browser window resizes. We may want to
     // update the maximum height of the dialog and scale the WebUI to the new
     // height. |size| is not set because the dialog is auto-resizeable.