[observatory] Sort native allocation profiles by size.

runtime/observatory/lib/src/cpu_profile/cpu_profile.dart

Index: runtime/observatory/lib/src/cpu_profile/cpu_profile.dart
diff --git a/runtime/observatory/lib/src/cpu_profile/cpu_profile.dart b/runtime/observatory/lib/src/cpu_profile/cpu_profile.dart
index 747d7b9ca9b1da8dfc3fcda55d4b400d6436c632..76e1a2680f6bdbbaad8e09abe52ad3703e5bfea0 100644
--- a/runtime/observatory/lib/src/cpu_profile/cpu_profile.dart
+++ b/runtime/observatory/lib/src/cpu_profile/cpu_profile.dart
@@ -104,6 +104,9 @@ class CodeCallTree extends CallTree<CodeCallTreeNode>
     for (var child in node.children) {
       _setCodeMemoryPercentage(node, child);
     }
+    node.children.sort((a, b) {
+      return b.inclusiveNativeAllocations - a.inclusiveNativeAllocations;
+    });
   }
 
   _recordCallerAndCalleesInner(
@@ -416,6 +419,9 @@ class FunctionCallTree extends CallTree implements M.FunctionCallTree {
     for (var child in node.children) {
       _setFunctionMemoryPercentage(node, child);
     }
+    node.children.sort((a, b) {
+      return b.inclusiveNativeAllocations - a.inclusiveNativeAllocations;
+    });
   }
 
   _markFunctionCallsInner(