[turbofan] Drop V8_TURBOFAN_BACKEND and V8_TURBOFAN_TARGET defines.

src/compiler/pipeline.h

Index: src/compiler/pipeline.h
diff --git a/src/compiler/pipeline.h b/src/compiler/pipeline.h
index 240ff69f59c58d46c57e3d5180e1125981db9aa7..15ed8a0e373dd5ee8a33f60311b67e28a9e8a2b1 100644
--- a/src/compiler/pipeline.h
+++ b/src/compiler/pipeline.h
@@ -46,9 +46,6 @@ class Pipeline {
                                           InstructionSequence* sequence,
                                           bool run_verifier);
 
-  static inline bool SupportedBackend() { return V8_TURBOFAN_BACKEND != 0; }
-  static inline bool SupportedTarget() { return V8_TURBOFAN_TARGET != 0; }
-
  private:
   static Handle<Code> GenerateCodeForTesting(CompilationInfo* info,
                                              CallDescriptor* call_descriptor,