Make it possible to launch chrome --mash with ozone_platform={wayland|x11}, chromeos=0

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index 9b2ca0d0d4f32b231024ea9e99af548a24f248f5..79e75d2284c31b4b8e587a6686744228e1e7fca0 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -892,7 +892,7 @@ content::BrowserMainParts* ChromeContentBrowserClient::CreateBrowserMainParts(
   // Construct additional browser parts. Stages are called in the order in
   // which they are added.
 #if defined(TOOLKIT_VIEWS)
-#if defined(OS_LINUX) && !defined(OS_CHROMEOS)
+#if defined(OS_LINUX) && !defined(OS_CHROMEOS) && !defined(USE_OZONE)
   main_parts->AddParts(new ChromeBrowserMainExtraPartsViewsLinux());

[Tom (Use chromium acct), 2016/10/17 23:40:52]

I'm a bit worried about this.  ChromeBrowserMainExtraPartsViewsLinux sets up
LinuxUI with the gtk2 ui, which is used mainly for theming.

I feel like we would still want this for wayland on desktop.  Gtk has a wayland
backend (might be only gtk3 or later), so we should still be able to use it.

Alternatively, we could stub out a LinuxUI for ozone for now.  rjkroege@ what do
you think?

[tonikitoo, 2016/10/18 04:55:06]

Here are the reasons to originally ifdef'out the gtk2 entry point,
ChromeBrowserMainExtraPartsViewsLinux:

1) the gtk2 theming code is already not build for use_ozone (see the related
snippet from chrome/browser/ui/BUILD.gn)

  (..)
  if (use_aura && !use_ozone && is_desktop_linux) {
    deps += [
      # gtk2 is the only component that can interact with gtk2 in our new
      # world.
      "//chrome/browser/ui/libgtk2ui",
    ]
  }
  (..)

2) glib itself is disabled for ozone builds (see the related snippet from
build/config/ui.gni):

  (..)
  # Turn off glib if Ozone is enabled.
  if (use_ozone) {
    use_glib = false
  }
  (..)

PS: should/can gtk{2,3} work with glib support disabled?

I also thought of stub'ing LinuxUI out, but given that LinuxUI class has so many
pure virtual methods, and this CL is a "bring up" CL, it seemed not the best
approach.

 #else
   main_parts->AddParts(new ChromeBrowserMainExtraPartsViews());