Added isolate + thread high watermark tracking to Observatory

runtime/vm/thread_registry.cc

Index: runtime/vm/thread_registry.cc
diff --git a/runtime/vm/thread_registry.cc b/runtime/vm/thread_registry.cc
index eb39501bc0db930332b1975252287f3673306a72..2e914cac6575a588ec9ac31b75041b752b2d4787 100644
--- a/runtime/vm/thread_registry.cc
+++ b/runtime/vm/thread_registry.cc
@@ -146,6 +146,7 @@ Thread* ThreadRegistry::GetFromFreelistLocked(Isolate* isolate) {
   return thread;
 }
 
+
 void ThreadRegistry::ReturnToFreelistLocked(Thread* thread) {
   ASSERT(thread != NULL);
   ASSERT(thread->os_thread_ == NULL);
@@ -157,4 +158,16 @@ void ThreadRegistry::ReturnToFreelistLocked(Thread* thread) {
   free_list_ = thread;
 }
 
+
+intptr_t ThreadRegistry::ThreadHighWatermarksTotalLocked() const {
+  ASSERT(threads_lock()->IsOwnedByCurrentThread());
+  intptr_t max_memory_usage_total = 0;
+  Thread* current = active_list_;
+  while (current != NULL) {
+    max_memory_usage_total += current->GetThreadHighWatermark();
+    current = current->next_;
+  }
+  return max_memory_usage_total;
+}
+
 }  // namespace dart