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Currently the logs were being uploaded at each chrome process restart.
Upload at most K logs in any X hours window. This prevents log uploading at start of each chrome process. Local state of chrome process is maintained across reboots. Maintained a List of uploads made in the previous X hour window.
UpdateLocalStateForLogs() keeps the logs updated for previous X hour window and appends if any upload is made recently.

The unit test makes K+3 uploads consecutively, and checks if delay of first K uploads is 0 and for the remaining uploads it is approximately X.
Another unit test checks that immediate log upload is not throttled.
Initial Commit

Bug: 789481
Change-Id: I16cadf69e68d8982b5b2384aebbeb6cdad892d2e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1876092
Commit-Queue: Swapnil Gupta <swapnilgupta@google.com>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Ivan Šandrk <isandrk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713395}