er, from *lines* that weren't changed, not from *files* that weren't changed.

Ooh, very good case study in what can go wrong right now.

We are planning to add filtering for lines that weren't changed ( bug 767856 ), and it seems this is going to be pretty important.

Even when we do that though, it's conceivable that someone will make a CL with thousands of files, with hundreds of lines with the same violation repeated over and over. 

In addition to filtering out comments in unchanged lines ( bug 767856 ), I propose another change:

If the number of comments to report for an analyzer exceeds some number (10? 50? 100?), convert the line comments to file-level comments with summaries, such as "Analyzer Foo found N results in this file.".

I think this seems reasonable since we're already planning to transform the output from analyzers before posting to Gerrit; we're not promising that the results from the analyzer are *always necessarily* exactly what's posted to Gerrit. And we shouldn't assume that analyzers won't accidentally produce thousands of comments.

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/81cf5de278089054705671123e4d0a478b62743a

commit 81cf5de278089054705671123e4d0a478b62743a
Author: Quinten Yearsley <qyearsley@chromium.org>
Date: Fri Apr 06 01:06:39 2018

In gerrit/rpc_report_results abort comments when there are too many

The advantages of this over https://crrev.com/c/996492 are:
 - It seems like a more related place to put it
 - The comments are stored (and may be useful for debugging)
 - Testing is simpler

Bug:  828406 
Change-Id: I9ae3a212e68fc7a037dc5ba45610a0bde1ea57d1
Reviewed-on: https://chromium-review.googlesource.com/999120
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
Reviewed-by: Marc-Antoine Ruel <maruel@chromium.org>

[modify] https://crrev.com/81cf5de278089054705671123e4d0a478b62743a/go/src/infra/tricium/appengine/gerrit/gerrit.infra_testing
[modify] https://crrev.com/81cf5de278089054705671123e4d0a478b62743a/go/src/infra/tricium/appengine/gerrit/rpc_report_results.go
[modify] https://crrev.com/81cf5de278089054705671123e4d0a478b62743a/go/src/infra/tricium/appengine/gerrit/rpc_report_results_test.go

This new behavior should take effect after the next deploy.

New version deployed, test CL: https://chromium-review.googlesource.com/c/playground/gerrit-tricium/demo/+/1003596

Test CL behaved as expected now -- Tricium reports that there were many results, but they're not posted to Gerrit.