DevTools isn't being downloaded like typical JavaScript, so bundle size concerns don't apply. Parsing is still a consideration (so I'm open for discussion here) but I think this change would provide a couple of benefits:
* People are more likely to *actually read* non-minified source code when e.g. a breakpoint is hit (as with the recent debugger statement)
* Component stacks will be easier to parse on bug reports
This commit adds a new tab to the Settings modal: Debugging
This new tab has the append component stacks feature and a new one: break on warn
This new feature adds a debugger statement into the console override
* DevTools console override handles new component stack format
DevTools does not attempt to mimic the default browser console format for its component stacks but it does properly detect the new format for Chrome, Firefox, and Safari.
* Enable prefer-const rule
Stylistically I don't like this but Closure Compiler takes advantage of
this information.
* Auto-fix lints
* Manually fix the remaining callsites
Update various parts of DevTools to account for the fact that the global "hook" might be undefined if DevTools didn't inject it (due to the page's `contentType`) it (due to the page's `contentType`)
* Updated DevTools local development instructions to mention experimental build step
* Added a command to download latest experimental release (for DevTools)
* Updated build instructions for clarity
* Added build-for-devtools package alias
* Added rudimentary context menu hook and menu UI
* Added backend support for copying a value at a specific path for the inspected element
* Added backend support for storing a value (at a specified path) as a global variable
* Added special casing to enable copying undefined/unserializable values to the clipboard
* Added copy and store-as-global context menu options to selected element props panel
* Store global variables separately, with auto-incremented name (like browsers do)
* Added tests for new copy and store-as-global backend functions
* Fixed some ownerDocument/contentWindow edge cases
* Refactored context menu to support dynamic options
Used this mechanism to add a conditional menu option for inspecting the current value (if it's a function)
* Renamed "safeSerialize" to "serializeToString" and added inline comment
PR #16752 changed how we were injecting the backend script to be done by the content script in order to work around Trusted Type limitations with our previous approach. This may have caused a regression (see #16840) so I'm backing it out to verify.
