Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtk2ui/gtk2_ui.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/libgtk2ui/gtk2_ui.h"
 
 #include <math.h>
 #include <pango/pango.h>
 #include <X11/Xcursor/Xcursor.h>
 #include <set>
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
 #include "base/environment.h"
 #include "base/i18n/rtl.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/nix/mime_util_xdg.h"
 #include "base/nix/xdg_util.h"
 #include "base/stl_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringprintf.h"
-#include "chrome/browser/themes/theme_properties.h"
+#include "chrome/browser/themes/theme_properties.h"  // nogncheck

[Elliot Glaysher, 2016/10/25 21:48:57]

What's the nogncheck here for?

[Tom (Use chromium acct), 2016/10/25 22:00:23]

Without it, if I run gn gen --check, I get this error:

ERROR at //chrome/browser/ui/libgtk2ui/gtk2_ui.cc:24:11: Include not allowed.
#include "chrome/browser/themes/theme_properties.h"
          ^---------------------------------------
It is not in any dependency of
  //chrome/browser/ui/libgtk2ui:libgtk2ui
The include file is in the target(s):
  //chrome/browser:browser
which should somehow be reachable.


Might be related to the removal of allow_circular_includes_from in
chrome/browser/BUILD.gn

[Tom (Use chromium acct), 2016/10/25 22:41:46]

dpranke@:
Me and erg@ discussed this offline and we're not confident that nogncheck here
is the right solution.  I was hitting other problems when preserving
'allow_circular_includes_from'.

There's nothing we actually need to link against from theme_properties.h, it's
just a bunch of enums.  Maybe we can split the constants out?

[Dirk Pranke, 2016/10/25 23:56:10]

nogncheck is indeed the wrong solution :). 

It is subverting the intent and hiding a layering violation (i.e., you're not
actually fixing the circular
dependency). See the docs for `gn check` for more. The right thing to do is to
move theme_properties.h into a separate source_set() target that the libgtk2ui
targets depend on.

[Tom (Use chromium acct), 2016/10/26 18:20:01]

Done.

 #include "chrome/browser/ui/libgtk2ui/app_indicator_icon.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_event_loop.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_key_bindings_handler.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_status_icon.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_util.h"
 #include "chrome/browser/ui/libgtk2ui/native_theme_gtk2.h"
 #include "chrome/browser/ui/libgtk2ui/print_dialog_gtk2.h"
 #include "chrome/browser/ui/libgtk2ui/printing_gtk2_util.h"
 #include "chrome/browser/ui/libgtk2ui/select_file_dialog_impl.h"
 #include "chrome/browser/ui/libgtk2ui/skia_utils_gtk2.h"
@@ skipping 1047 matching lines @@
   // Blacklist scaling factors <130% (crbug.com/484400) and round
   // to 1 decimal to prevent rendering problems (crbug.com/485183).
   return scale < 1.3f ? 1.0f : roundf(scale * 10) / 10;
 }
 
 }  // namespace libgtk2ui
 
 views::LinuxUI* BuildGtk2UI() {
   return new libgtk2ui::Gtk2UI;
 }