remove WebMediaPlayerImpl::CreateRenderer
remove WebMediaPlayerImpl::CreateRenderer

WebMediaPlayerImpl::CreateRenderer is neither defined or called anywhere, remove it's declaration.

Review URL: https://codereview.chromium.org/1487653003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#362468}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk