Enhancement description - Previously the charts use Google Charts for rendering which requires an internet connection to work. This is a limitation of the Google visualisation technology. The alternative seems to be to offer a different visualisation technology like C3/D3 js in BC. So, Google Charts library has been replaced by C3 and C3 is the default chart library in BC.
C3 on BC link.
As per vidya_iyengar's email titled "Appformer scrum BAPLs" - "this has a customer ticket attached, hence P1 for 7.3."
BAPL link: https://issues.jboss.org/browse/BAPL-564