Problem/Motivation
The discussion in #2120875: Remove breakpoint and picture module from core was resolved by closing that discussion but marking as needing to be revisited before D8 beta. A number of issues were identified that needed to be addressed in the Picture and Breakpoints modules. This issue is intended to track those and any new issues that arise before beta.
Fixed issues
#1828606: Make BREAKPOINT resources inheritable
#1851018: Improve breakpoint configuration implementation.
#1883526: Decide on the picture polyfill to use
#2026319: Mis-named variables in picture_theme()
#2030653: Expand ResponsiveImageMapping with methods
#2078001: Modernize responsive_image.module forms
#2124377: Rename "Picture" module to "Responsive Image" module
#2132551: Picture module uses config keys with a dot
#2204159: (Responsive) Image styles do not add correct cache tags, nor do they invalidate cache tags upon flushing
#2211831: Removal of alt attribute from [picture] tag
#2222431: Project name clean up after Picture module renamed Responsive Image
#2225677: Fix naming in ResponsiveImageMappingEntityTest following module rename from Picture to Responsive Image
#2227435: Remove noscript from picture element markup
#2243549: Text changes needed as follow-up to Menu UI module rename
#2245727: Add missing configuration schema in Breakpoint component
Open issues
#1701112: Advanced responsive images UI/UX for breakpoints
#1701116: Responsive Images UI/UX: Image styles
#1820512: Move Breakpoint module closer to meeting Drupal standards
#1836860: Picture doesn't work with ajax callback
#1855412: Enable responsive_image.module by default for standard install profile.
#1880606: Introduce a configuration UI for theme-based breakpoints
#1898442: responsive_image.module - Convert theme_ functions to Twig
#1937914: Special handling for setting the BreakpointGroup::breakpoints property during ConfigStorageController::importChange()
#1945228: Repetitive config in breakpoint.module
#1945362: error messages on admin page for picture mappings
#1971174: BreakpointGroup::loadAllBreakpoints() is expensive
#1982818: Automatically sort breakpoints from small to large
#1999312: Add an 'empty image' option for responsive image
#2030585: Expand Breakpoint with methods
#2030587: Expand BreakpointGroup with methods
#2123225: Do not upscale by default
#2123251: DX of outputting picture elements is pretty bad
#2203459: responsive_image mapping doesn't implement 'delete' function
#2219329: ResponsiveImageMapping::mappings and ResponsiveImageMapping::breakpointGroup properties have inconsistent return structure and type respectively
#2220865: Add empty img element inside picture element
#2254071: Responsive images can't be linked to Content
#2260061: [PP-1] Implement Picture polyfill 2.1
#2264571: Add an 'original image' option for picture
#2271529: Move breakpoint settings to theme and module *.breakpoints.yml files at root level