[heap-profiler] Fix a bug in MergeNames function.

Bug: chromium:811925
Change-Id: I0b2d9562fa77d6d198a689769705a2d5e977abf9
Reviewed-on: https://chromium-review.googlesource.com/928701Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51432}

src/profiler/heap-snapshot-generator.cc

@@ -2045,7 +2045,7 @@ HeapEntry::Type EmbedderGraphNodeType(EmbedderGraphImpl::Node* node) {
 // Otherwise, the result is the embedder node name.
 const char* MergeNames(StringsStorage* names, const char* embedder_name,
                        const char* wrapper_name) {
-  for (const char* suffix = wrapper_name; suffix; suffix++) {
+  for (const char* suffix = wrapper_name; *suffix; suffix++) {
     if (*suffix == '/') {
       return names->GetFormatted("%s %s", embedder_name, suffix);
     }

test/cctest/test-heap-profiler.cc

@@ -2938,6 +2938,14 @@ void BuildEmbedderGraphWithWrapperNode(v8::Isolate* v8_isolate,
       graph->AddNode(std::unique_ptr<Node>(new EmbedderNode("OtherNode", 20)));
   graph->AddEdge(global_node, embedder_node);
   graph->AddEdge(wrapper_node, other_node);
+
+  Node* wrapper_node2 = graph->AddNode(
+      std::unique_ptr<Node>(new EmbedderNode("WrapperNode2", 10)));
+  Node* embedder_node2 = graph->AddNode(std::unique_ptr<Node>(
+      new EmbedderNode("EmbedderNode2", 10, wrapper_node2)));
+  graph->AddEdge(global_node, embedder_node2);
+  graph->AddEdge(embedder_node2, wrapper_node2);
+  graph->AddEdge(wrapper_node2, other_node);
 }
 
 TEST(EmbedderGraphWithWrapperNode) {
@@ -2963,6 +2971,14 @@ TEST(EmbedderGraphWithWrapperNode) {
   const v8::HeapGraphNode* wrapper_node =
       GetChildByName(embedder_node, "WrapperNode / TAG");
   CHECK(!wrapper_node);
+
+  const v8::HeapGraphNode* embedder_node2 =
+      GetChildByName(global, "EmbedderNode2");
+  other_node = GetChildByName(embedder_node2, "OtherNode");
+  CHECK(other_node);
+  const v8::HeapGraphNode* wrapper_node2 =
+      GetChildByName(embedder_node, "WrapperNode2");
+  CHECK(!wrapper_node2);
 }
 
 static inline i::Address ToAddress(int n) {