Fix RegExp.prototype.compile.length to be 2

SpiderMonkey switched to 2, test262 tests for 2, and 2 is a reasonable, natural
value.

R=yangguo

Review URL: https://codereview.chromium.org/1616233002

Cr-Commit-Position: refs/heads/master@{#33504}

src/js/regexp.js

@@ -693,9 +693,6 @@ utils.InstallGetter(GlobalRegExp.prototype, 'ignoreCase', RegExpGetIgnoreCase);
 utils.InstallGetter(GlobalRegExp.prototype, 'multiline', RegExpGetMultiline);
 utils.InstallGetter(GlobalRegExp.prototype, 'source', RegExpGetSource);
 
-// The length of compile is 1 in SpiderMonkey.
-%FunctionSetLength(GlobalRegExp.prototype.compile, 1);
-
 // The properties `input` and `$_` are aliases for each other.  When this
 // value is set the value it is set to is coerced to a string.
 // Getter and setter for the input.

test/mjsunit/regexp-compile.js

@@ -40,3 +40,5 @@ assertEquals(["x", "x"], re.exec("axyb"));
 re.compile("(y)");
 
 assertEquals(["y", "y"], re.exec("axyb"));
+
+assertEquals(2, re.compile.length);