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Because we're using mojo data pipe, which has own quota control,
to transfer received data, we don't have manual one, or
mojom::WebSocket.AddReceiveFlowControlQuota().
This CL does a sort of work removing the function.

mojom::WebSocket.AddReceiveFlowControlQuota(quota) did 5 tasks:
browser side(mainly on WebSocketChannel)
 1. Trigger the first ReadFrame if renderer gets not throttled.
For #1, this patch moves the trigger to mojo WebSocket.StartReceiving.

 2. Trigger next ReadFrame if there is enough quota.
 3. Send pending dataframes based on added quota.
This patch moves task #2 and #3 to websocket.cc and datapipe itself.

 4. Dropchannel if all pending frames are received by renderer when closed.
Because we can care #4 w/o renderer ping back, this patch move
RespondToClosingHandshake()to WebSocketChannel::ReadFrames().

renderer side(mainly on WebSocketChannelImpl)
 5. Ping browser that backpressure is turned off.
For task #5, this patch changes not to call the mojo but throttle
datapipe reading with WebSocketHandleImpl::ConsumePendingDataFrames().

receive-arraybuffer-1MBx100.htmll?iteration=100 measurement on local build:
ToT:            144 MB/s (stdev: 4.56 MB/s)
Patch:          208 MB/s (stdev: 6.15 MB/s)
  (+44% to ToT, +41% to ReadOnlyBuffer)
ReadOnlyBuffer: 147 MB/s

Change-Id: I61feab06f0e3719520e6a47eea61e0322e4da01f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1763507
Commit-Queue: Yoichi Osato <yoichio@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691072}