H264/HEVC QP bitstream parsing relocated to WebProcess

Component: WebKit WebRTC codecs | f10733e

WebKit's GPU Process performs hardware video encode/decode via VideoToolbox and is more privileged than the sandboxed WebContent process. The QP (quantization parameter) of an encoded frame is read from the raw H.264/HEVC Annex B bitstream and fed into WebRTC's rate-control/statistics in LibWebRTCCodecs, which lives in WebProcess. This commit removes the H264BitstreamParser/HEVCBitstreamParser members and QP-extraction calls from GPUVideoEncoderVTBH264/H265, moving QP parsing into LibWebRTCCodecs::completedEncoding.

Significance

Bitstream parsing is removed from the GPU Process and runs only where consumed (WebRTC stats in WebProcess), with explicitly no behavior change. The completion callback passes raw bytes and the Encoder into toWebKitEncodedFrameInfo(), which parses and overwrites info.qp only when webRTCWebCoreVideoCodecsEnabled is on. Since the GPU Process already sends the encoded bytes to WebProcess for delivery, this removes a capability from the more privileged process without adding a data flow.

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