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

src/v8.cc

Index: src/v8.cc
diff --git a/src/v8.cc b/src/v8.cc
index 7d2294ee0cf1ba6b4d19acccabac4bce04e6558c..31d2dd579d66e880dd294b0d45efd8903cb7c701 100644
--- a/src/v8.cc
+++ b/src/v8.cc
@@ -54,7 +54,6 @@ bool V8::is_running_ = false;
 bool V8::has_been_set_up_ = false;
 bool V8::has_been_disposed_ = false;
 bool V8::has_fatal_error_ = false;
-bool V8::use_crankshaft_ = true;
 List<CallCompletedCallback>* V8::call_completed_callbacks_ = NULL;
 v8::ArrayBuffer::Allocator* V8::array_buffer_allocator_ = NULL;
 
@@ -318,9 +317,6 @@ void V8::InitializeOncePerProcessImpl() {
   OS::SetUp();
   Sampler::SetUp();
   CPU::SetUp();
-  use_crankshaft_ = FLAG_crankshaft
-      && !Serializer::enabled()
-      && CPU::SupportsCrankshaft();
   OS::PostSetUp();
   ElementsAccessor::InitializeOncePerProcess();
   LOperand::SetUpCaches();