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I missed a few callsites to WaitForChildFrameSurfaceReady which were in Android tests.
This change updates them to use the new HitTestRegionObserver

TEST=TouchSelectionControllerClientAndroidSiteIsolationTest.BasicSelectionIsolatedIframe
SitePerProcessHitTestBrowserTest.CrossProcessTooltipTestAndroid

Bug: 787945
Change-Id: I0abfa8e4c036552ac416909b15398a53a71ee064
Reviewed-on: https://chromium-review.googlesource.com/1102829Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568059}