Add immune spaces abstraction

ImmuneSpaces is a set of spaces which are not reclaimable by the GC in
the current collection. This set of spaces does not have requirements
about space adjacency like the old ImmuneRegion. ImmuneSpaces generates
the largest immune region for the GC. Since there is no requirement on
adjacency, it is possible to have multiple non-adjacent applicaton
image files.

For image spaces, we also look at the oat code which is normally after
the application image. In this case, we add the code as part of the
immune region. This is required to have both the boot image and the
zygote space be in the same immune region (for performance reasons).

Bug: 22858531

Change-Id: I5103b31c0e39ad63c594f5557fc848a3b288b43e
diff --git a/runtime/gc/collector/mark_sweep.h b/runtime/gc/collector/mark_sweep.h
index 8f7df78..245f96b 100644
--- a/runtime/gc/collector/mark_sweep.h
+++ b/runtime/gc/collector/mark_sweep.h
@@ -26,7 +26,7 @@
 #include "garbage_collector.h"
 #include "gc_root.h"
 #include "gc/accounting/heap_bitmap.h"
-#include "immune_region.h"
+#include "immune_spaces.h"
 #include "object_callbacks.h"
 #include "offsets.h"
 
@@ -314,8 +314,9 @@
 
   accounting::ObjectStack* mark_stack_;
 
-  // Immune region, every object inside the immune range is assumed to be marked.
-  ImmuneRegion immune_region_;
+  // Every object inside the immune spaces is assumed to be marked. Immune spaces that aren't in the
+  // immune region are handled by the normal marking logic.
+  ImmuneSpaces immune_spaces_;
 
   // Parallel finger.
   AtomicInteger atomic_finger_;