Update GraphicsLayerTest.applyScrollToScrollableArea
Update GraphicsLayerTest.applyScrollToScrollableArea

WebLayer::setScrollOffset no longer calls GraphicsLayer::didScroll().
See https://chromiumcodereview.appspot.com/15984005

TBR=jamesr@chromium.org
BUG=247279

Review URL: https://codereview.chromium.org/16562009

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@151968 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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