[es6] Use SubString in String{Starts,Ends}With
Much faster and constant than always searching the whole string
````
var allCodePoints = [];
for (var i = 0; i < 65536; i++) allCodePoints[i] = i;
var allCharsString = String.fromCharCode.apply(String, allCodePoints);
function bench(search) {
var counter = 0;
print(search + " found at " + allCharsString.startsWith(search));
var start = Date.now();
while (counter++ < 5000000) {
allCharsString.startsWith(search);
}
var end = Date.now();
print(end - start);
return counter;
}
print("single character");
bench("\u0000");
bench("\u0050");
bench("\u1000");
````
OLD
single character
found at true
374
P found at false
559
က found at false
13492
NEW
single character
found at true
261
P found at false
146
က found at false
146
BUG=v8:4384
LOG=N
Review URL: https://codereview.chromium.org/
1321853006
Cr-Commit-Position: refs/heads/master@{#30599}