Roll V8 back to 3.6

Roll back to V8 3.6 to fix x86 build, we don't have ucontext.h.

This reverts commits:
5d4cdbf7a67d3662fa0bee4efdb7edd8daec9b0b
c7cc028aaeedbbfa11c11d0b7b243b3d9e837ed9
592a9fc1d8ea420377a2e7efd0600e20b058be2b

Bug: 5688872
Change-Id: Ic961bb5e65b778e98bbfb71cce71d99fa949e995
diff --git a/src/v8threads.cc b/src/v8threads.cc
index fd8d536..3881d66 100644
--- a/src/v8threads.cc
+++ b/src/v8threads.cc
@@ -154,7 +154,7 @@
 
 bool ThreadManager::RestoreThread() {
   ASSERT(IsLockedByCurrentThread());
-  // First check whether the current thread has been 'lazily archived', i.e.
+  // First check whether the current thread has been 'lazily archived', ie
   // not archived at all.  If that is the case we put the state storage we
   // had prepared back in the free list, since we didn't need it after all.
   if (lazily_archived_thread_.Equals(ThreadId::Current())) {