Add reporting of JS heap size limit to GetHeapStatistics.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 110468e2313ec75196b7c7604d6c2612ff09e922..36248437c789f569d53e4a1cd3b1cd5ea7ae5404 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -3299,7 +3299,8 @@ bool v8::V8::Dispose() {
 
 HeapStatistics::HeapStatistics(): total_heap_size_(0),
                                   total_heap_size_executable_(0),
-                                  used_heap_size_(0) { }
+                                  used_heap_size_(0),
+                                  heap_size_limit_(0) { }
 
 
 void v8::V8::GetHeapStatistics(HeapStatistics* heap_statistics) {
@@ -3307,6 +3308,7 @@ void v8::V8::GetHeapStatistics(HeapStatistics* heap_statistics) {
   heap_statistics->set_total_heap_size_executable(
       i::Heap::CommittedMemoryExecutable());
   heap_statistics->set_used_heap_size(i::Heap::SizeOfObjects());
+  heap_statistics->set_heap_size_limit(i::Heap::MaxReserved());
 }