Add Metrics for heap high water marks

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
diff --git a/runtime/vm/pages.cc b/runtime/vm/pages.cc
index 24846526ea75a43a2a1ee3d4bed777410d137193..390f452e858c5fa21febe736d742b9bb0c03724b 100644
--- a/runtime/vm/pages.cc
+++ b/runtime/vm/pages.cc
@@ -169,6 +169,8 @@ PageSpace::PageSpace(Heap* heap,
                              FLAG_old_gen_growth_time_ratio),
       gc_time_micros_(0),
       collections_(0) {
+  // We aren't holding the lock but no one can reference us yet.
+  UpdateMaxCapacityLocked();
 }
 
 
@@ -532,6 +534,15 @@ void PageSpace::AbandonBumpAllocation() {
 }
 
 
+void PageSpace::UpdateMaxCapacityLocked() {
+  ASSERT(heap_ != NULL);
+  ASSERT(heap_->isolate() != NULL);
+  Isolate* isolate = heap_->isolate();
+  isolate->GetHeapOldCapacityMaxMetric()->SetValue(
+      static_cast<int64_t>(usage_.capacity_in_words) * kWordSize);
+}
+
+
 bool PageSpace::Contains(uword addr) const {
   for (ExclusivePageIterator it(this); !it.Done(); it.Advance()) {
     if (it.page()->Contains(addr)) {