Fold HTypeInfoReadVariable of instance creation.
Fold HTypeInfoReadVariable of instance creation.

This often replaces an expensive substitution read with a re-use of an indexed read, e.g.:

    t1 = H.setRuntimeTypeInfo(
        new H.WhereIterable(
            t1,
            new Q.CompositeView_removeChild_closure(view)),
        [H.getTypeArgumentByIndex(t1, 0)]);
    this.childViews = P.List_List$from(
        t1,
        true,
        H.getRuntimeTypeArgument(t1, "Iterable", 0));

---->

    t2 = H.getTypeArgumentByIndex(t1, 0);
    this.childViews = P.List_List$from(
        H.setRuntimeTypeInfo(
            new H.WhereIterable(
                t1,
                new Q.CompositeView_removeChild_closure(view)),
            [t2]),
        true,
        t2);

R=sigmund@google.com

Review URL: https://codereview.chromium.org/2272923002 .

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