Revert "lazy instantiation of the default isolate" and "build fix for 17049".

src/v8.h

Index: src/v8.h
diff --git a/src/v8.h b/src/v8.h
index 47403d9ecb35b45684bdcde6ba4ed1c8bfbba7d2..5848f748185e27c7ce4ceaaf1deaccf139d24a7b 100644
--- a/src/v8.h
+++ b/src/v8.h
@@ -81,7 +81,7 @@ class V8 : public AllStatic {
   // initial state is created by reading the deserialized data into an
   // empty heap.
   static bool Initialize(Deserializer* des);
-  static bool TearDown();
+  static void TearDown();
 
   // Report process out of memory. Implementation found in api.cc.
   static void FatalProcessOutOfMemory(const char* location,