Revert change 5989, which causes failures in some benchmarks.

src/hydrogen.cc

 // Copyright 2010 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 4063 matching lines @@
 
 bool HGraphBuilder::TryMathFunctionInline(Call* expr) {
   // Try to inline calls like Math.* as operations in the calling function.
   MathFunctionId id = expr->target()->shared()->math_function_id();
   int argument_count = expr->arguments()->length() + 1;  // Plus receiver.
   switch (id) {
     case kMathRound:
     case kMathFloor:
     case kMathAbs:
     case kMathSqrt:
-    case kMathLog:
       if (argument_count == 2) {
         HValue* argument = Pop();
         Drop(1);  // Receiver.
         HUnaryMathOperation* op = new HUnaryMathOperation(argument, id);
         op->set_position(expr->position());
         ast_context()->ReturnInstruction(op, expr->id());
         return true;
       }
       break;
     case kMathPow:
@@ skipping 1571 matching lines @@
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify();
   if (chunk_ != NULL) chunk_->Verify();
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal