x11, ozone/linux: Initialize GTK after Ozone

GtkUi is currently already used in Ozone X11. Ozone platform
initialization code calls XInitThreads() function to init Xlib in
threaded mode under certain conditions**, which according to the docs
should be called before any other Xlib call [1].  However, GTK is
initialized before Ozone platform, which makes Gtk to create/init X11
connection object before calling XInitThreads(), that's wrong and causes
crashes when Gtk file dialogs are instantiated/shown (among other
potential issues not observed so far).

Present CL simplifies GtkUi initialization, moving it entirely to
ToolkitInitialized() override, which happens just after aura::Env's
initialization (which actually init OzonePlatform global object) and
before initializing Views framework, so that code previously in
PreCreateThreads() could be moved and unified under in a single method.

As follow-up, crrev.com/c/1863940 fixes the remaining issues that were
preventing file dialogs to work in Ozone X11.

** Actually current Ozone X11 calls it always, but that must be changed
soon to do so only in some cases. E.g: in-process-gpu, single-process,
etc. Issue tracked under https://crbug.com/1024477.

[1] https://www.x.org/releases/X11R7.5/doc/man/man3/XInitThreads.3.html

Bug: 1008755
Change-Id: Idc81e94dc236257bd7693bfe13833239bbb0fa87
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1899796
Commit-Queue: Nick Yamane <nickdiego@igalia.com>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Michael Spang <spang@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#716908}

chrome/browser/ui/views/chrome_browser_main_extra_parts_views_linux.cc

@@ -15,7 +15,9 @@ ChromeBrowserMainExtraPartsViewsLinux::ChromeBrowserMainExtraPartsViewsLinux() =
 ChromeBrowserMainExtraPartsViewsLinux::
     ~ChromeBrowserMainExtraPartsViewsLinux() = default;
 
-void ChromeBrowserMainExtraPartsViewsLinux::PreEarlyInitialization() {
+void ChromeBrowserMainExtraPartsViewsLinux::ToolkitInitialized() {
+  ChromeBrowserMainExtraPartsViews::ToolkitInitialized();
+
   views::LinuxUI* linux_ui = views::BuildLinuxUI();
   if (!linux_ui)
     return;
@@ -27,21 +29,11 @@ void ChromeBrowserMainExtraPartsViewsLinux::PreEarlyInitialization() {
         return ThemeServiceAuraLinux::ShouldUseSystemThemeForProfile(
             GetThemeProfileForWindow(window));
       }));
-  views::LinuxUI::SetInstance(linux_ui);
-}
 
-void ChromeBrowserMainExtraPartsViewsLinux::ToolkitInitialized() {
-  ChromeBrowserMainExtraPartsViews::ToolkitInitialized();
-  auto* instance = views::LinuxUI::instance();
-  if (instance)
-    instance->Initialize();
-}
-
-void ChromeBrowserMainExtraPartsViewsLinux::PreCreateThreads() {
   // Update the device scale factor before initializing views
   // because its display::Screen instance depends on it.
-  auto* instance = views::LinuxUI::instance();
-  if (instance)
-    instance->UpdateDeviceScaleFactor();
-  ChromeBrowserMainExtraPartsViews::PreCreateThreads();
+  linux_ui->UpdateDeviceScaleFactor();
+
+  views::LinuxUI::SetInstance(linux_ui);
+  linux_ui->Initialize();
 }

chrome/browser/ui/views/chrome_browser_main_extra_parts_views_linux.h

@@ -21,9 +21,7 @@ class ChromeBrowserMainExtraPartsViewsLinux
   ~ChromeBrowserMainExtraPartsViewsLinux() override;
 
   // Overridden from ChromeBrowserMainExtraParts:
-  void PreEarlyInitialization() override;
   void ToolkitInitialized() override;
-  void PreCreateThreads() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainExtraPartsViewsLinux);

ui/ozone/platform/x11/ozone_platform_x11.cc

@@ -13,7 +13,8 @@
 #include "ui/display/fake/fake_display_delegate.h"
 #include "ui/events/devices/x11/touch_factory_x11.h"
 #include "ui/events/platform/x11/x11_event_source_default.h"
-#include "ui/gfx/x/x11.h"
+#include "ui/gfx/x/x11_connection.h"
+#include "ui/gfx/x/x11_types.h"
 #include "ui/ozone/common/stub_overlay_manager.h"
 #include "ui/ozone/platform/x11/x11_clipboard_ozone.h"
 #include "ui/ozone/platform/x11/x11_cursor_factory_ozone.h"
@@ -148,7 +149,8 @@ class OzonePlatformX11 : public OzonePlatform {
 
     // Always initialize in multi-thread mode, since this is used only during
     // development.
-    XInitThreads();
+    // TODO(crbug.com/1024477): Initialize Xlib threads only when required
+    gfx::InitializeThreadedX11();
 
     // If XOpenDisplay() failed there is nothing we can do. Crash here instead
     // of crashing later. If you are crashing here, make sure there is an X