Fixes mojo max size problem

[NejcZdovc]

Resolves brave/brave-browser#8691

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
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  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protection-Mode
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
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Test Plan:

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on.
• All relevant documentation has been updated.

[bsclifton]

As noted on Slack, I don't think this solution is correct

Ideal solution would be either:

• building batch of records one at a time (storing how many bytes total so far), until max bytes reached
• knowing maximum size of a publisher record and dividing the GetConfiguration().max_message_num_bytes number by this max size

[NejcZdovc]

@bsclifton this one is just testing if this is a problem or not. It's not a final fix

[bsclifton]

For sure 😄 Just left the note in case I was going to sleep before the conclusion

[bsclifton]

Reviewed with @NejcZdovc - intention of this PR is to "stop the bleeding"

The limits here are much lower. We believe the Banner limit is what was causing a problem. We talked with teammates and determined that max publisher record size is 104 bytes (each) and max banner record size (each) is 1,543.

With limit set (before this PR) of 150,000... this results in 231,450,000 which is larger than the max size (GetConfiguration().max_message_num_bytes) which is 134,217,728. New size (max record count 80,000) is 123,440,000 (not counting the mojo message details)

There of course will be extra bytes since the messages themselves are encoded. This needs to be determined and accounted for

This PR puts us under the safe limits for both. Impact will be verified list takes longer to be realized- but it will stop the CPU problem and crashing problem (on Nightly and Beta)

When PR builder finishes, we can verify the binary that is created to ensure problem is gone 👍

[bsclifton]

Thanks to @mkarolin for finding the CHECK that was failing in https://cs.chromium.org/chromium/src/mojo/core/node_channel.cc?l=765&rcl=6f416959b64ac147d12ab8fd5d0bc71d8201537b

[NejcZdovc]

confirming that CPU is not a problem anymore after this fix

[bsclifton]

Cherry-picked to 1.7 with 0ddb199