Don't crash when reporting an access check failure for a detached global proxy (Chromium issue 475884).

Use smaller heap growing factor in idle notification to start incremental marking when there is idle time >16ms (Chromium issue 477323).

Performance and stability improvements on all platforms.

Cr-Commit-Position: refs/heads/4.4.23@{#1}
Cr-Branched-From: 04b72aa09ffbe81a6fd91443fed91af62ca71292-refs/heads/master@{#27901}