Update V8 to r5716 as required by WebKit r70949

Change-Id: I0d5cd05bb0427af33e5c9f6efdc209366a32bde3
diff --git a/test/cctest/test-log.cc b/test/cctest/test-log.cc
index 16d0f00..7168737 100644
--- a/test/cctest/test-log.cc
+++ b/test/cctest/test-log.cc
@@ -337,8 +337,8 @@
 }
 
 
-// Profiling multiple threads that use V8 is currently only available on Linux.
-#ifdef __linux__
+// BUG(913). Need to implement support for profiling multiple VM threads.
+#if 0
 
 namespace {