deps: upgrade V8 to 5.0.71.32

* Pick up the branch head for V8 5.0 stable [1]
* Edit v8 gitignore to allow trace_event copy
* Update V8 DEP trace_event as per deps/v8/DEPS [2]

[1] https://chromium.googlesource.com/v8/v8.git/+/3c67831
[2] https://chromium.googlesource.com/chromium/src/base/trace_event/common/+/4b09207e447ae5bd34643b4c6321bee7b76d35f9

Ref: https://github.com/nodejs/node/pull/5945
PR-URL: https://github.com/nodejs/node/pull/6111
Reviewed-By: targos - Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: indutny - Fedor Indutny <fedor.indutny@gmail.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/deps/v8/src/compiler/graph-trimmer.h b/deps/v8/src/compiler/graph-trimmer.h
index d8258becc8..98d335a44d 100644
--- a/deps/v8/src/compiler/graph-trimmer.h
+++ b/deps/v8/src/compiler/graph-trimmer.h
@@ -28,14 +28,18 @@ class GraphTrimmer final {
   // or any of the roots in the sequence [{begin},{end}[.
   template <typename ForwardIterator>
   void TrimGraph(ForwardIterator begin, ForwardIterator end) {
-    while (begin != end) MarkAsLive(*begin++);
+    while (begin != end) {
+      Node* const node = *begin++;
+      if (!node->IsDead()) MarkAsLive(node);
+    }
     TrimGraph();
   }
 
  private:
   V8_INLINE bool IsLive(Node* const node) { return is_live_.Get(node); }
   V8_INLINE void MarkAsLive(Node* const node) {
-    if (!node->IsDead() && !IsLive(node)) {
+    DCHECK(!node->IsDead());
+    if (!IsLive(node)) {
       is_live_.Set(node, true);
       live_.push_back(node);
     }