Use std:: on symbols declared in C++-style C headers.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 4e614d875218f2c48f7f050d6ea8680d7de9533d..2060d2e2f909e350c6fad8855406ca4bd3a64f6f 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -3898,7 +3898,7 @@ HInstruction* HUnaryMathOperation::New(
       case kMathExp:
         return H_CONSTANT_DOUBLE(fast_exp(d));
       case kMathLog:
-        return H_CONSTANT_DOUBLE(log(d));
+        return H_CONSTANT_DOUBLE(std::log(d));
       case kMathSqrt:
         return H_CONSTANT_DOUBLE(fast_sqrt(d));
       case kMathPowHalf:
@@ -3911,9 +3911,9 @@ HInstruction* HUnaryMathOperation::New(
         // Doubles are represented as Significant * 2 ^ Exponent. If the
         // Exponent is not negative, the double value is already an integer.
         if (Double(d).Exponent() >= 0) return H_CONSTANT_DOUBLE(d);
-        return H_CONSTANT_DOUBLE(floor(d + 0.5));
+        return H_CONSTANT_DOUBLE(std::floor(d + 0.5));
       case kMathFloor:
-        return H_CONSTANT_DOUBLE(floor(d));
+        return H_CONSTANT_DOUBLE(std::floor(d));
       default:
         UNREACHABLE();
         break;