Sync the URL constructor with the spec

third_party/WebKit/Source/core/dom/URL.idl

 /*
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  * Copyright (C) 2012 Motorola Mobility Inc.
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 // https://url.spec.whatwg.org/#url
 
 [
-    // TODO(philipj): There should only be one constructor:
-    // Constructor(USVString url, optional USVString base)
-    Constructor(USVString url),
-    Constructor(USVString url, USVString base),
-    Constructor(USVString url, URL base),
+    Constructor(USVString url, optional USVString base),
     Exposed=(Window,Worker),
     ImplementedAs=DOMURL,
     RaisesException=Constructor,
     GarbageCollected,
 ] interface URL {
     // TODO(philipj): Implement domainToASCII() and domainToUnicode().
     // crbug.com/493908
     // static USVString domainToASCII(USVString domain);
     // static USVString domainToUnicode(USVString domain);
 
     // TODO(philipj): This should be in a partial interface definition:
     // File API
     // https://w3c.github.io/FileAPI/#creating-revoking
     // TODO(philipj): Neither the return value nor the argument should be nullable.
     [RaisesException, CallWith=ExecutionContext] static DOMString? createObjectURL(Blob? blob);
     [CallWith=ExecutionContext] static void revokeObjectURL(DOMString url);
 };
 
 URL implements URLUtils;