8159818: Convert IHOP_test to GTest
Reviewed-by: tschatzl, iignatyev

8142484: Let IHOP follow the current capacity, not the maximum capacity
Summary: Instead of following the current heap capacity, let all IHOP calculations follow the maximum capacity.
Reviewed-by: brutisso, jmasa

8136679: JFR event for adaptive IHOP
Reviewed-by: tbenson, mgerdin, sangheki, ehelin

8136678: Implement adaptive sizing algorithm for IHOP
Summary: Add adaptive sizing for IHOP that maximizes throughput (starts marking as late as possible). This functionality is enabled using a new -XX:+G1AdaptiveIHOP switch (default: false).
Reviewed-by: mgerdin, jmasa, pliden

8136681: Factor out IHOP calculation from G1CollectorPolicy
Summary: Move out existing IHOP value calculation into an implementation of a new interface called G1IHOPControl. Prepare for changes to accomodate adaptive IHOP implementation.
Reviewed-by: jmasa, mgerdin, ehelin