Enabling page visibility api in the chrome browser.

BUG=83286
TEST=None.


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=86569

Review URL: http://codereview.chromium.org/7036019

git-svn-id: http://src.chromium.org/svn/trunk/src/build@86881 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

features_override.gypi

@@ -46,6 +46,7 @@
       'ENABLE_OFFLINE_WEB_APPLICATIONS=1',
       'ENABLE_OPENTYPE_SANITIZER=1',
       'ENABLE_ORIENTATION_EVENTS=0',
+      'ENABLE_PAGE_VISIBILITY_API=1',
       'ENABLE_PROGRESS_TAG=1',
       'ENABLE_QUOTA=1',
       'ENABLE_REQUEST_ANIMATION_FRAME=1',