compositor_unittests target is unimplmented on Mac

ui/gfx/compositor/compositor.gyp

Index: ui/gfx/compositor/compositor.gyp
diff --git a/ui/gfx/compositor/compositor.gyp b/ui/gfx/compositor/compositor.gyp
index db00d380d75f15f93af0178a4f7cc6eeacde1e3f..8f20ea34ce0ad0893db3a6211f157aa31d77a4ab 100644
--- a/ui/gfx/compositor/compositor.gyp
+++ b/ui/gfx/compositor/compositor.gyp
@@ -61,7 +61,7 @@
         'screen_rotation.h',
       ],
       'conditions': [
-        ['os_posix == 1 and OS != "mac"', {
+        ['os_posix == 1', {
           'sources!': [
             'compositor_stub.cc',
           ],
@@ -91,7 +91,7 @@
         }],
         ['use_webkit_compositor == 1', {
             'sources/': [
-              ['exclude', '^compositor_(gl|win|stub).(h|cc)$'],
+              ['exclude', '^compositor_(gl|mac|win|stub).(h|cc|mm)$'],
             ],
             'dependencies': [
               '<(DEPTH)/webkit/support/webkit_support.gyp:fileapi',
@@ -120,11 +120,15 @@
       'conditions': [
         ['use_webkit_compositor == 1', {
             'dependencies': [
-              '<(DEPTH)/base/allocator/allocator.gyp:allocator',
               '<(DEPTH)/webkit/support/webkit_support.gyp:webkit_support',
               '<(DEPTH)/third_party/WebKit/Source/WebKit/chromium/WebKit.gyp:webkit',
             ],
         }],
+        ['use_webkit_compositor == 1 and OS != "mac"', {
+            'dependencies': [
+              '<(DEPTH)/base/allocator/allocator.gyp:allocator',
+            ],
+        }],
       ],
     },
     {
@@ -152,6 +156,7 @@
         'run_all_unittests.cc',
         'test_compositor_host.h',
         'test_compositor_host_linux.cc',
+        'test_compositor_host_mac.mm',
         'test_compositor_host_win.cc',
         'test_layer_animation_delegate.cc',
         'test_layer_animation_delegate.h',