Fix asserts and GC unsafeness in stub generation, bug=1689.

src/x64/code-stubs-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3318 matching lines @@
 }
 
 
 void CodeStub::GenerateStubsAheadOfTime() {
   CEntryStub save_doubles(1);
   save_doubles.SaveDoubles();
   save_doubles.GetCode();
 }
 
 
+void CodeStub::GenerateFPStubs() {
+}
+
+
 void CEntryStub::GenerateThrowTOS(MacroAssembler* masm) {
   // Throw exception in eax.
   __ Throw(rax);
 }
 
 
 void CEntryStub::GenerateCore(MacroAssembler* masm,
                               Label* throw_normal_exception,
                               Label* throw_termination_exception,
                               Label* throw_out_of_memory_exception,
@@ skipping 2161 matching lines @@
   __ Drop(1);
   __ ret(2 * kPointerSize);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64