Ignore soft heap limit when reserving space.

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1324 matching lines @@
   // True if we have reached the allocation limit in the old generation that
   // should force the next GC (caused normally) to be a full one.
   inline bool OldGenerationPromotionLimitReached() {
     return PromotedTotalSize() > old_gen_promotion_limit_;
   }
 
   inline intptr_t OldGenerationSpaceAvailable() {
     return old_gen_allocation_limit_ - PromotedTotalSize();
   }
 
+  inline intptr_t OldGenerationCapacityAvailable() {
+    return max_old_generation_size_ - PromotedTotalSize();
+  }
+
   static const intptr_t kMinimumPromotionLimit = 5 * Page::kPageSize;
   static const intptr_t kMinimumAllocationLimit =
       8 * (Page::kPageSize > MB ? Page::kPageSize : MB);
 
   // When we sweep lazily we initially guess that there is no garbage on the
   // heap and set the limits for the next GC accordingly.  As we sweep we find
   // out that some of the pages contained garbage and we have to adjust
   // downwards the size of the heap.  This means the limits that control the
   // timing of the next GC also need to be adjusted downwards.
   void LowerOldGenLimits(intptr_t adjustment) {
@@ skipping 1306 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_