Add hot memory usage to memory graph.

Docker-DCO-1.1-Signed-off-by: Rohit Jnagal <jnagal@google.com> (github: rjnagal)
Merge remote-tracking branch 'upstream/master'

Docker-DCO-1.1-Signed-off-by: Rohit Jnagal <jnagal@google.com> (github: rjnagal)
Merge pull request #195 from rjnagal/master

Add hot memory usage to memory graph.