Add methods to enable configuration of ResourceConstraints based on limits derived at runtime.

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
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@@ skipping 2319 matching lines @@
   static const int kMaxMarkSweepsInIdleRound = 7;
   static const int kIdleScavengeThreshold = 5;
 
   // Shared state read by the scavenge collector and set by ScavengeObject.
   PromotionQueue promotion_queue_;
 
   // Flag is set when the heap has been configured.  The heap can be repeatedly
   // configured through the API until it is set up.
   bool configured_;
 
+  // Flag is set if the heap has been configured with any value different from
+  // the default values.
+  bool limits_changed_from_defaults_;

[Hannes Payer (out of office), 2013/09/19 14:50:57]

Why do we need that? If the embedder decides to overwrite multiple times that
should be ok? Or is there a problem?

[rmcilroy, 2013/09/19 15:01:34]

This is not to prevent the embedder overwriting things multiple times (that's
fine, and still works after this CL), it is to prevent the is_memory_constrained
flag resetting the default values if the embedder has already changed the values
from their defaults (i.e., if the embedder specifically sets limits, treat the
preferentially to any changes which would be incurred by setting the
is_memory_constrained flag).

+
   ExternalStringTable external_string_table_;
 
   VisitorDispatchTable<ScavengingCallback> scavenging_visitors_table_;
 
   MemoryChunk* chunks_queued_for_free_;
 
   Mutex* relocation_mutex_;
 #ifdef DEBUG
   bool relocation_mutex_locked_by_optimizer_thread_;
 #endif  // DEBUG;
@@ skipping 673 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_