Fix Math.log10 implementation for 1 - Number.EPSILON.

test/mjsunit/es6/math-log2-log10.js

 // Copyright 2013 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 32 matching lines @@
 
 for (var i = -310; i <= 308; i += 0.5) {
   assertEquals(i, Math.log10(Math.pow(10, i)));
   // Square roots are tested below.
   if (i != -0.5 && i != 0.5) assertEquals(i, Math.log2(Math.pow(2, i)));
 }
 
 // Test denormals.
 assertEquals(-307.77759430519706, Math.log10(1.5 * Math.pow(2, -1023)));
 
+// Issue 4025.  Remove delta once issue 4029 has been fixed.
+assertEqualsDelta(-9.643274665532873e-17, Math.log10(1-Number.EPSILON), 3e-32);
+
 // Test Math.log2(2^k) for -1074 <= k <= 1023.
 var n = -1074;
 // This loop covers n from -1074 to -1043
 for (var lowbits = 1; lowbits <= 0x80000000; lowbits *= 2) {
   var x = %_ConstructDouble(0, lowbits);
   assertEquals(n, Math.log2(x));
   n++;
 }
 // This loop covers n from -1042 to -1023
 for (var hibits = 1; hibits <= 0x80000; hibits *= 2) {
@@ skipping 27 matching lines @@
 }
 
 x = Math.pow(2, -100);
 for (var k = 0; k < 1000; ++k) {
   var y = Math.log2(x);
   var expected = Math.log(x) / Math.LN2;
   var err = Math.abs(y - expected) / expected;
   assertEqualsDelta(0, err, 1e-15);
   x *= 1.1;
 }