Adjust heuristics for idle notifications after context disposal.

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index df3717e4faee7bb650dfb006fcdd32742a14c7e4..afc068942a205954501823bb0ac6833501c7da34 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1960,9 +1960,25 @@ class Heap {
     return incremental_marking()->WorthActivating();
   }
 
+  // Estimates how many milliseconds a Mark-Sweep would take to complete.
+  // In idle notification handler we assume that this function will return:
+  // - a number less than 1000 for any heap size.

[Erik Corry, 2012/03/20 08:16:00]

We should either make sure that this is true, or make sure that we do not assume
it.  I would prefer the latter.

+  // - a number less than 10 for small heaps, which are less than 8Mb.
+  // - a number greater than 10 for large heaps, which are greater than 32Mb.
+  int TimeMarkSweepWouldTakeInMs() {
+    // Rough estimate of how many megabytes of heap can be processed in 1 ms.
+    static const int kMbPerMs = 2;
+
+    int heap_size_mb = static_cast<int>(SizeOfObjects() / MB);
+    return heap_size_mb / kMbPerMs;
+  }
+
   // Returns true if no more GC work is left.
   bool IdleGlobalGC();
 
+  void AdvanceIdleIncrementalMarking(intptr_t step_size);
+
+
   static const int kInitialSymbolTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
   static const int kInitialNumberStringCacheSize = 256;