cc: Add frame timing request plumbing through the layers.

This patch adds frame timing request class, which contains a rect and
an id for that rect. Furthermore, it adds plumbing so that the requests
get propagated from the original Layer into both pending and active
LayerImpls. Verified using tracing that the requests appear correctly.

R=danakj, michaelblain@chromium.org
BUG=441555

Review URL: https://codereview.chromium.org/834343004

Cr-Commit-Position: refs/heads/master@{#313093}

• cc/BUILD.gn[diff]
• cc/cc.gyp[diff]
• cc/debug/frame_timing_request.cc[Added - diff]
• cc/debug/frame_timing_request.h[Added - diff]
• cc/layers/layer.cc[diff]
• cc/layers/layer.h[diff]
• cc/layers/layer_impl.cc[diff]
• cc/layers/layer_impl.h[diff]