Add GN build file for ui/base target.

In Debug config:

$ gn gen out/Debug_gn

$ ninja -C out/Debug_gn ui_base

In Release config:

$ gn gen out/Release_gn --args='is_debug=false'

$ ninja -C out/Release_gn ui_base

BUG=None
TEST=see above
R=brettw@chromium.org
TBR=ben

Review URL: https://codereview.chromium.org/250823008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266836 0039d316-1c4b-4281-b951-d872f2087c98

BUILD.gn

@@ -49,6 +49,7 @@ group("root") {
     "//third_party/WebKit/Source/wtf",
     "//third_party/zlib",
     "//tools/gn",
+    "//ui/base:ui_base",
     "//ui/base/strings",
     "//ui/events",
     "//ui/gfx",
@@ -72,6 +73,7 @@ group("root") {
       "//third_party/libusb",
       "//third_party/WebKit/Source/wtf",  # TODO(brettw) re-enable for Android.
       "//tools/gn",
+      "//ui/base:ui_base",
       "//ui/events",
       "//ui/gfx",
     ]

ui/base/ui_base.gyp

@@ -247,6 +247,7 @@
         'touch/touch_editing_controller.h',
         'touch/touch_enabled.cc',
         'touch/touch_enabled.h',
+        'ui_base_export.h',
         'ui_base_exports.cc',
         'ui_base_paths.cc',
         'ui_base_paths.h',
@@ -256,7 +257,6 @@
         'ui_base_switches_util.h',
         'ui_base_types.cc',
         'ui_base_types.h',
-        'ui_base_export.h',
         'view_prop.cc',
         'view_prop.h',
         'webui/jstemplate_builder.cc',