aura: A few changes to have aura_demo compile and run on linux.

aura/aura.gyp

 # Copyright (c) 2011 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
       'target_name': 'aura',
-      'type': 'static_library',
+      'type': '<(component)',
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:base_i18n',
         '../skia/skia.gyp:skia',
         '../ui/gfx/compositor/compositor.gyp:compositor',
         '../ui/ui.gyp:gfx_resources',
         '../ui/ui.gyp:ui',
         '../ui/ui.gyp:ui_resources',
       ],
+      'defines': [
+        'AURA_IMPLEMENTATION',
+      ],
       'sources': [
         'desktop_host.h',
         'desktop_host_linux.cc',
         'desktop_host_win.cc',
         'desktop_host_win.h',
         'desktop.cc',
         'desktop.h',
         'event.cc',
         'event.h',
         'event_win.cc',
+        'event_x.cc',
         'focus_manager.cc',
         'focus_manager.h',
         'hit_test.h',
         'root_window.cc',
         'root_window.h',
         'window.cc',
         'window.h',
         'window_delegate.h',
         'window_manager.cc',
         'window_manager.h',
@@ skipping 42 matching lines @@
         'window_unittest.cc',
         'run_all_unittests.cc',
         'test_suite.cc',
         'test_suite.h',
         '<(SHARED_INTERMEDIATE_DIR)/ui/gfx/gfx_resources.rc',
         '<(SHARED_INTERMEDIATE_DIR)/ui/ui_resources/ui_resources.rc',
       ],
     },
   ],
 }