Summary: An update buffer is not processed correctly, which causes roots into the collection set not to be scanned and, hence, for the heap to be corrupted. The cause is that an object is accessed after it has been explicitly deleted, which causes a race.
Reviewed-by: jcoomes, ysr

6622418: G1: assert(false,"Non-balanced monitor enter/exit!") fails
Summary: The mark-sweep compact (which we use for full gc) wrapper did not save the mark words for biased locked objects.  The fix is to trivially call the appropriate methods.
Reviewed-by: tonyp, ysr

Summary: Under certain circumstances, two cleanup threads can claim and process the same region.
Reviewed-by: apetrusenko, ysr

6652160: G1: assert(cur_used_bytes == _g1->recalculate_used(),"It should!") at g1CollectorPolicy.cpp:1425
Summary: In attempt_allocation_slow() wait for the concurrent cleanup to complete before modifying _summary_bytes_used.
Reviewed-by: jmasa, apetrusenko

6723570: G1: assertion failure: p == current_top or oop(p)->is_oop(),"p is not a block start" (revisited!)
Summary: Fixed the incorrect assigment to G1OffsetTableContigSpace::_gc_time_stamp. Also added a little more paranoia to operations on a global timestamp.
Reviewed-by: tonyp

6702387: G1: assertion failure: assert(p == current_top || oop(p)->is_oop(),"p is not a block start")
Summary: Do not coalesce dead and moved objects when removing self-forwarding pointers during the evacuation failure. Also fixed a issue in a BOT refinement code for TLABs.
Reviewed-by: tonyp, jcoomes

Summary: experimental() flags will protect features of an experimental nature that are not supported in the regular product build. Made UseG1GC an experimental flag.
Reviewed-by: jmasa, kamg, coleenp

6710665: G1: guarantee(_cm->out_of_regions() && _cm->region_stack_empty() && _task_queue->size() == 0, ...)
Summary: Remove the incorrect assumptions from guarantee()s.
Reviewed-by: ysr, tonyp

Summary: First mercurial integration of the code for the Garbage-First garbage collector.
Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr