🏗 Add new task gulp codecov-upload to upload coverage reports

[rsimha]

This PR does the following:

• Moves code coverage uploading from tasks/runtime-test into a new task gulp codecov-upload
• Fixes a bug where ads, tests, and third party code were being factored into the calculation of total coverage
• No longer uploads when tests fail, thereby preventing incorrect / partial reports (Codecov is posting comments on PRs even though comments are disabled #20480)

Partial fix for #22507
Fixes #20480

[rsimha]

This worked.

Logs: https://travis-ci.org/ampproject/amphtml/jobs/537581032#L1636
Report: https://codecov.io/gh/ampproject/amphtml/commit/1eab084

[estherkim]

I like the bug fixes! One thought though - I don't think uploading code coverage reports should be decoupled from generating these reports. Especially if it's only something that Travis does... it's more of a util function that immediately follows the report generation, not its own gulp task. What do you think?

Also, should I wait for this PR to merge before starting #22507?

[rsimha]

I don't think uploading code coverage reports should be decoupled from generating these reports. Especially if it's only something that Travis does... it's more of a util function that immediately follows the report generation, not its own gulp task. What do you think?

Today, code coverage is generated and uploaded separately from two places: unit and integration tests. The server then merges the sources to generate a single report. This poses a problem when one of the two test runs fails, resulting in a noisy coverage chart for our repo.

Decoupling uploading from generating solves this problem by making sure all sources have generated coverage data before uploading them once and for all.

Also, should I wait for this PR to merge before starting #22507?

It'll be slightly easier if this were to be merged first, but not a blocker.

[codecov]

Codecov Report

Merging #22515 into master will decrease coverage by 6.94%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #22515      +/-   ##
==========================================
- Coverage   85.61%   78.67%   -6.95%     
==========================================
  Files        1556      794     -762     
  Lines      145994    49485   -96509     
==========================================
- Hits       124987    38930   -86057     
+ Misses      21007    10555   -10452

Flag	Coverage Δ
#integration_tests	31.8% <ø> (-9.26%)	⬇️
#unit_tests	78.05% <ø> (-7.7%)	⬇️

Impacted Files	Coverage Δ
extensions/amp-story/1.0/amp-story-page.js	66.04% <0%> (-0.54%)	⬇️
extensions/amp-story/1.0/amp-story.js	77.83% <0%> (-0.13%)	⬇️
test/unit/utils/test-array.js
ads/bidtellect.js
test/unit/test-custom-element.js
...pan-zoom/0.1/test/integration/test-amp-pan-zoom.js
test/unit/test-ie-media-bug.js
...t/unit/inabox/test-inabox-frame-overlay-manager.js
...xtensions/amp-bind/0.1/test/test-bind-validator.js
...p-analytics/0.1/test/test-transport-serializers.js
... and 761 more

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[rsimha]

Merging #22515 into master will decrease coverage by 6.94%.

This is expected, since we were erroneously including ads, tests, and third party code in the coverage numbers. The new (more accurate) baseline coupled with status reports (that can be made to require a minimum patch-level coverage) will help us drive up this number.