Move GL one-off initialization code.

ui/gl/init/BUILD.gn

Index: ui/gl/init/BUILD.gn
diff --git a/ui/gl/init/BUILD.gn b/ui/gl/init/BUILD.gn
index 844ee291e5d59c58f1791c1913ba5f7f295d3965..48301dd1c035c6940b0cb2d6b6c02df55355e7d4 100644
--- a/ui/gl/init/BUILD.gn
+++ b/ui/gl/init/BUILD.gn
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/ui.gni")
+
 component("init") {
   output_name = "gl_init"
 
@@ -9,6 +11,8 @@ component("init") {
     "gl_factory.cc",
     "gl_factory.h",
     "gl_init_export.h",
+    "gl_initializer.cc",
+    "gl_initializer.h",
   ]
   defines = [ "GL_INIT_IMPLEMENTATION" ]
 
@@ -20,4 +24,16 @@ component("init") {
   public_deps = [
     "//ui/gl",
   ]
+
+  if (is_android) {
+    sources += [ "gl_initializer_android.cc" ]
+  } else if (is_win) {
+    sources += [ "gl_initializer_win.cc" ]
+  } else if (is_mac) {
+    sources += [ "gl_initializer_mac.cc" ]
+  } else if (use_x11) {
+    sources += [ "gl_initializer_x11.cc" ]
+  } else if (use_ozone) {
+    sources += [ "gl_initializer_ozone.cc" ]
+  }
 }