Remove use_libcc_for_compositor gyp variable

We flipped the default to 1 a few weeks ago and the tree doesn't compile with
this set to 0. Time to go!

BUG=


Review URL: https://chromiumcodereview.appspot.com/11066132

git-svn-id: http://src.chromium.org/svn/trunk/src/build@162049 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -671,9 +671,6 @@
     # Use system yasm instead of bundled one.
     'use_system_yasm%': 0,
 
-    # Use compositor implementation in cc/ instead of in WebKit.
-    'use_libcc_for_compositor%': 1,
-
     # Default to enabled PIE; this is important for ASLR but we may need to be
     # able to turn it off for various reasons.
     'linux_disable_pie%': 0,