Move global V8::IsDead() into the Isolate.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 9220a6a93d6718889add651968ecc712c6a54737..5de7f82b52ad97468076b3c11e468961cb2dabc5 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -1059,6 +1059,9 @@ class Isolate {
     thread_local_top_.top_lookup_result_ = top;
   }
 
+  bool IsDead() { return has_fatal_error_; }
+  void SignalFatalError() { has_fatal_error_ = true; }
+
   bool use_crankshaft() { return use_crankshaft_; }
 
   bool initialized_from_snapshot() { return initialized_from_snapshot_; }
@@ -1302,6 +1305,9 @@ class Isolate {
   unibrow::Mapping<unibrow::Ecma262Canonicalize> interp_canonicalize_mapping_;
   CodeStubInterfaceDescriptor* code_stub_interface_descriptors_;
 
+  // True if fatal error has been signaled for this isolate.
+  bool has_fatal_error_;
+
   // True if we are using the Crankshaft optimizing compiler.
   bool use_crankshaft_;