[builtins] Introduce proper Float64Cos and Float64Sin.

src/base/ieee754.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_BASE_IEEE754_H_
 #define V8_BASE_IEEE754_H_
 
 namespace v8 {
 namespace base {
 namespace ieee754 {
 
 // Returns the principal value of the arc tangent of |x|; that is the value
 // whose tangent is |x|.
 double atan(double x);
 
 // Returns the principal value of the arc tangent of |y/x|, using the signs of
 // the two arguments to determine the quadrant of the result.
 double atan2(double y, double x);
 
+// Returns the cosine of |x|, where |x| is given in radians.
+double cos(double x);
+
 // Returns the base-e exponential of |x|.
 double exp(double x);
 
 double atanh(double x);
 
 // Returns the natural logarithm of |x|.
 double log(double x);
 
 // Returns a value equivalent to |log(1+x)|, but computed in a way that is
 // accurate even if the value of |x| is near zero.
 double log1p(double x);
 
-// Return the base 2 logarithm of |x|.
+// Returns the base 2 logarithm of |x|.
 double log2(double x);
 
-// Return the base 10 logarithm of |x|.
+// Returns the base 10 logarithm of |x|.
 double log10(double x);
 
-// Return cube root of |x|.
+// Returns the cube root of |x|.
 double cbrt(double x);
 
 // Returns exp(x)-1, the exponential of |x| minus 1.
 double expm1(double x);
 
+// Returns the sine of |x|, where |x| is given in radians.
+double sin(double x);
+
 }  // namespace ieee754
 }  // namespace base
 }  // namespace v8
 
 #endif  // V8_BASE_IEEE754_H_