Cr-UI-Browser-Downloads : Despite the name, this covers all issues related to downloading a file except saving entire pages (which is Cr-Blink-SavePage), not just UI issues. Most downloads bugs will have the word “download” or “save as” in the description. Issues with the HTTP server for the Chrome binaries are not downloads bugs.
Cr-UI-Browser-SafeBrowsing : Bugs that have to do with the process by which a URL or file is determined to be dangerous based on our databases, or the resulting interstitials. Determination of danger based purely on content-type or file extension belongs in Cr-UI-Browser-Downloads, not SafeBrowsing.
Cr-Internals-Network-SSL : This includes issues that should be also tagged as Cr-Security-UX (certificate error pages or other security interstitials, omnibox indicators that a page is secure), and more general SSL issues. If you see requests that die in the SSL negotiation phase, in particular, this is often the correct label.
Cr-Internals-Network-DataProxy : Flywheel / the Data Reduction Proxy. Issues require “Reduce Data Usage” be turned on. Proxy url is https://proxy.googlezip.net:443, with http://compress.googlezip.net:80 as a fallback. Currently Android and iOS only.
Cr-Internals-Network-Cache : The cache is the layer that handles most range request logic (Though range requests may also be issued by the PDF plugin, XHRs, or other components).
Cr-Internals-Network-SPDY : Covers HTTP2 as well.
Cr-Internals-Network-HTTP : Typically not used. Unclear what it covers, and there's no specific HTTP owner.
Cr-Internals-Network-Logging : Covers about:net-internals, about:net-export as well as the what's sent to the NetLog.
Cr-Internals-Network-Connectivity : Issues related to switching between networks, ERR_NETWORK_CHANGED, Chrome thinking it‘s online when it’s not / navigator.onLine inaccuracies, etc.
Cr-Internals-Network-Filters : Covers SDCH and gzip issues. ERR_CONTENT_DECODING_FAILED indicates a problem at this layer, and bugs here can also cause response body corruption.
Bugs in these areas often receive the Cr-Internals-Network label, though they fall largely outside the purview of the network stack team:
Cr-Blink-Forms : Issues submitting forms, forms having weird data, forms sending the wrong method, etc.
Cr-Blink-Loader : Cross origin issues are sometimes loader related. Blink also has an in-memory cache, and when it‘s used, requests don’t appear in about:net-internals. Requests for the same URL are also often merged there as well. This does not cover issues with content/browser/loader/ files.
Cr-Blink-XHR : Generic issues with sync/async XHR requests - missing request or response headers, multiple headers, etc. These will often run into issues in certain corner cases (Cross origin / CORS, proxy, whatever). Attach all labels that seem appropriate.
Cr-Services-Sync : Sharing data/tabs/history/passwords/etc between machines not working.
Cr-Platform-Extensions : Issues extensions loading / not loading / hanging.
Cr-Platform-Extensions-API : Issues with network related extension APIs should have this label. chrome.webRequest is the big one, I believe, but there are others.
Cr-UI-Browser-Omnibox : Basically any issue with the omnibox. URLs being treated as search queries rather than navigations, dropdown results being weird, not handling certain unicode characters, etc. If the issue is new TLDs not being recognized by the omnibox, that‘s due to Chrome’s TLD list being out of date, and not an omnibox issue. Such TLD issues should be duped against http://crbug.com/37436.
Cr-Internals-Media-Network : Issues related to media. These often run into the 6 requests per hostname issue, and also have fun interactions with the cache, particularly in the range request case.
Cr-Internals-Plugins-PDF : Issues loading pdf files. These are often related to range requests, which also have some logic at the Internals-Network-Cache layer.
Cr-UI-Browser-History : Issues which only appear with forward/back navigation.
Cr-OS-Systems-Network / Cr-OS-Systems-Mobile / Cr-OS-Systems-Bluetooth : These should be used for issues with ChromeOS's platform network code, and not net/ issues on ChromeOS.
Cr-Blink-SecurityFeature : CORS / Cross origin issues. Main frame cross-origin navigation issues are often actually Cr-UI-Browser-Navigation issues.
Cr-Privacy : Privacy related bug (History, cookies discoverable by an entity that shouldn't be able to do so, incognito state being saved in memory or on disk beyond the lifetime of incognito tabs, etc). Generally used in conjunction with other labels.
Type-Bug-Security : Security related bug (Allows for code execution from remote site, allows crossing security boundaries, unchecked array bounds, etc).