Migrate content/common/gpu/media code to media/gpu
Migrate content/common/gpu/media code to media/gpu

This is part of a gpu & media refactor to enable proper layering for Mus. See bug for details.

BUG=586386

Committed: https://crrev.com/6e70beb84fe0d0a3d27e4369c8b6aaae001afb81
Cr-Commit-Position: refs/heads/master@{#390896}

Committed: https://crrev.com/0f54920173bda1d13e9c89c51a1995a8542c5648
Cr-Commit-Position: refs/heads/master@{#390897}

Review-Url: https://codereview.chromium.org/1882373004
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#390908}

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