Update VE core submodule to master (fc3c1b4)

New changes:
4166f91 Refactor debug bar dump methods and add hide button
1568e52 Record whitespace on generated empty paragraphs correctly
2253934 Fix whitespace consistency checking when child has no whitespace property
29b249f Improve support for multiple surfaces in demo

Change-Id: Ic496da654130a356530d6028a5fe4230d6c0c735
Merge "Update VE core submodule to master (fc3c1b4)"