Implement DOMTokenList.prototype.replace().

Firefox and Safari already shipped it.
This CL fixes 256 failing tests in external/wpt/.

Intent: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/0P4_WvNr1xY

Bug: 724906
Change-Id: Ic55ead1509afd3e631ed0251fa312bd5b4a7001f
Reviewed-on: https://chromium-review.googlesource.com/521002
Reviewed-by: Takayoshi Kochi <kochi@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#476240}

third_party/WebKit/LayoutTests/external/wpt/dom/interfaces-expected.txt

@@ -1,5 +1,5 @@
 This is a testharness.js-based test.
-Found 1570 tests; 1565 PASS, 5 FAIL, 0 TIMEOUT, 0 NOTRUN.
+Found 1570 tests; 1568 PASS, 2 FAIL, 0 TIMEOUT, 0 NOTRUN.
 PASS Test driver 
 PASS Event interface: existence and properties of interface object 
 PASS Event interface object length 
@@ -1550,7 +1550,7 @@ PASS DOMTokenList interface: operation contains(DOMString)
 PASS DOMTokenList interface: operation add(DOMString) 
 PASS DOMTokenList interface: operation remove(DOMString) 
 PASS DOMTokenList interface: operation toggle(DOMString,boolean) 
-FAIL DOMTokenList interface: operation replace(DOMString,DOMString) assert_own_property: interface prototype object missing non-static operation expected property "replace" missing
+PASS DOMTokenList interface: operation replace(DOMString,DOMString) 
 PASS DOMTokenList interface: operation supports(DOMString) 
 PASS DOMTokenList interface: attribute value 
 PASS DOMTokenList interface: stringifier 
@@ -1565,8 +1565,8 @@ PASS DOMTokenList interface: document.body.classList must inherit property "remo
 PASS DOMTokenList interface: calling remove(DOMString) on document.body.classList with too few arguments must throw TypeError 
 PASS DOMTokenList interface: document.body.classList must inherit property "toggle" with the proper type (5) 
 PASS DOMTokenList interface: calling toggle(DOMString,boolean) on document.body.classList with too few arguments must throw TypeError 
-FAIL DOMTokenList interface: document.body.classList must inherit property "replace" with the proper type (6) assert_inherits: property "replace" not found in prototype chain
-FAIL DOMTokenList interface: calling replace(DOMString,DOMString) on document.body.classList with too few arguments must throw TypeError assert_inherits: property "replace" not found in prototype chain
+PASS DOMTokenList interface: document.body.classList must inherit property "replace" with the proper type (6) 
+PASS DOMTokenList interface: calling replace(DOMString,DOMString) on document.body.classList with too few arguments must throw TypeError 
 PASS DOMTokenList interface: document.body.classList must inherit property "supports" with the proper type (7) 
 PASS DOMTokenList interface: calling supports(DOMString) on document.body.classList with too few arguments must throw TypeError 
 PASS DOMTokenList interface: document.body.classList must inherit property "value" with the proper type (8)