To make it easier to debug why sites aren't playing video when block autoplay is enabled, it would be useful to add more mozlogs to HTMLMediaElement to log when the JS exposed functions are called.

Comment on attachment 8952279 [details] Bug 1439473 - Improve logging of HTMLMediaElement JS API calls. https://reviewboard.mozilla.org/r/221526/#review228086 ::: dom/html/HTMLMediaElement.cpp:1957 (Diff revision 1) > +static nsCString > +DocumentOrigin(nsIDocument* aDoc) > +{ > + nsCOMPtr<nsIPrincipal> principal; > + nsCString origin; > + if (!aDoc || !(principal = aDoc->NodePrincipal()) || Nit: Personally not a fan of assignment inside an if stmt.

Comment on attachment 8952279 [details] Bug 1439473 - Improve logging of HTMLMediaElement JS API calls. https://reviewboard.mozilla.org/r/221526/#review228108 ::: dom/html/HTMLMediaElement.cpp:1957 (Diff revision 1) > +static nsCString > +DocumentOrigin(nsIDocument* aDoc) > +{ > + nsCOMPtr<nsIPrincipal> principal; > + nsCString origin; > + if (!aDoc || !(principal = aDoc->NodePrincipal()) || I expanded this function out to make it more explicit.

Pushed by cpearce@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/2d7a7976ee3a Improve logging of HTMLMediaElement JS API calls. r=kamidphish

backed out for bustage on HTMLMediaElement.cpp:4032 backout: https://hg.mozilla.org/integration/autoland/rev/1e76d991fe6ccf655bb75ddf75d8dd7e365a27b1 push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&revision=2d7a7976ee3a5579845076a23c512729438a0581 failure log: https://treeherder.mozilla.org/logviewer.html#?job_id=163603511&repo=autoland&lineNumber=21300 [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - In file included from /builds/worker/workspace/build/src/obj-firefox/dom/html/Unified_cpp_dom_html2.cpp:2: [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - /builds/worker/workspace/build/src/dom/html/HTMLMediaElement.cpp:4032:5: error: You must immediately return after calling this function [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - aRv.Throw(NS_ERROR_DOM_MEDIA_NOT_ALLOWED_ERR); [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - ^ [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - /builds/worker/workspace/build/src/dom/html/HTMLMediaElement.cpp:4043:5: error: You must immediately return after calling this function [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - aRv.Throw(NS_ERROR_DOM_MEDIA_NOT_SUPPORTED_ERR); [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - ^ [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - /builds/worker/workspace/build/src/dom/html/HTMLMediaElement.cpp:4096:9: error: You must immediately return after calling this function [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - aRv.Throw(rv); [task 2018-02-22T02:26:40.626Z] 02:26:40 INFO - ^ [task 2018-02-22T02:26:40.627Z] 02:26:40 INFO - 3 errors generated. [task 2018-02-22T02:26:40.627Z] 02:26:40 INFO - /builds/worker/workspace/build/src/config/rules.mk:1047: recipe for target 'Unified_cpp_dom_html2.o' failed [task 2018-02-22T02:26:40.627Z] 02:26:40 INFO - make[4]: *** [Unified_cpp_dom_html2.o] Error 1 [task 2018-02-22T02:26:40.627Z] 02:26:40 INFO - make[4]: Leaving directory '/builds/worker/workspace/build/src/obj-firefox/dom/html' [task 2018-02-22T02:26:40.627Z] 02:26:40 INFO - /builds/worker/workspace/build/src/config/recurse.mk:73: recipe for target 'dom/html/target' failed [task 2018-02-22T02:26:40.627Z] 02:26:40 INFO - make[3]: *** [dom/html/target] Error 2 [task 2018-02-22T02:26:40.627Z] 02:26:40 INFO - make[3]: *** Waiting for unfinished jobs....

Pushed by cpearce@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/d2a43ef3a3a6 Improve logging of HTMLMediaElement JS API calls. r=kamidphish