[builtins] Migrate Math.log to TurboFan.

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index f8c8cad16416abf6ae4a23b57f4ca91097d1b50b..765dda3f6dec6a6ce158568cbfcbebf09a9c4ce4 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -12781,15 +12781,6 @@ void HOptimizedGraphBuilder::GenerateMathPow(CallRuntime* call) {
 }
 
 
-void HOptimizedGraphBuilder::GenerateMathLogRT(CallRuntime* call) {
-  DCHECK(call->arguments()->length() == 1);
-  CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
-  HValue* value = Pop();
-  HInstruction* result = NewUncasted<HUnaryMathOperation>(value, kMathLog);
-  return ast_context()->ReturnInstruction(result, call->id());
-}
-
-
 void HOptimizedGraphBuilder::GenerateFixedArrayGet(CallRuntime* call) {
   DCHECK(call->arguments()->length() == 2);
   CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));