This reverts commit ae8be3cc.

Issue #2173655 by Cottser, xjm, jessebeach, alexpott, rlmumford: Refactor theme() to _theme(); make it a private API to discourage module developers from circumventing the renderable build system.

Issue #2068471 by dawehner, Crell, tim.plunkett, jibran, fubhy, larowlan: Normalize Controller/View-listener behavior with a Page object.

Issue #1954892 by dawehner, David_Rothstein, tim.plunkett: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system.

Revert "Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system."

This reverts commit fc04601c.

Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system.

Issue #1886448 by dawehner, sun, Berdir, ParisLiakos: Rewrite the theme registry into a proper service.

Issue #2049207 by dlu, blakehall, janstoeckler, ramlev, Moderate | Cottser: Replace .tpl.php with .html.twig in documentation.

Issue #1751194 by Cottser, mikl, effulgentsia, benjifisher: Introduce hook_theme_suggestions_HOOK() and hook_theme_suggestions_HOOK_alter().

Issue #1981368 by tim.plunkett, Crell, webchick: Convert all routes to 'module_name().foo_bar()' naming convention.

Issue #2004286 by joelpittet, jenlampton, Cottser, LinL: Defer calls to drupal_get_()* functions until printed inside a template by adding a RenderWrapper class.

Issue #2030457 by Mark Carver, Cottser: Fixed Warning: Missing argument 3 for template_preprocess() for theme functions overridden by templates.

Issue #1972514 by Wim Leers, effulgentsia, Gábor Hojtsy, ekl1773: Fixed Impossible to set attributes for all entities.

Issue #1806478 by Cottser, joelpittet, kevinquillen: Make twig the default engine once all modules templates are converted from .tpl.php to .html.twig.

Issue #1920886 by Cottser, Fabianx: Drupal_render() should only render the child elements when rendering a 'render element' for the first time.

Issue #575298 by sun, tim.plunkett, Rob Loach, KrisBulman, Jacine, danillonunes: Provide non-PHP way to reliably override CSS.

Issue #1168246 by sun, mgifford, Manuel Garcia, mbrett5062, ry5n, Everett Zufelt, nod_, aspilicious, deviantintegral, tim.plunkett: Freedom For Fieldsets! Long Live The DETAILS.

Issue #1696786 by Fabianx, jenlampton, stevector, steveoliver, jwilson3, amateescu, chx: Integrate Twig into core: Implementation issue.

Issue #1608878 by jessebeach, tim.plunkett, dead_arm, nod_, sun, effulgentsia, Everett Zufelt, geerlingguy: Added CTools dropbutton to core.

- Patch #1290694 by hefox, tlattimore, c4rl, chx, tim.plunkett, tstoeckler, msonnabaum: provide consistency for attributes and classes arrays provided by template_preprocess().

Issue #1443202 by TravisCarden, tim.plunkett, xjm: Make sure hook_preprocess documentation points to real funcions

Issue #1213536 by David_Rothstein, sun, effulgentsia, Yorirou: Fixed Non-resettable theme_get_registry() cache causes problems for non-interactive installations.

Issue #1430300 by mradcliffe, effulgentsia: Fixed Preprocess functions in an include file fail to get called when the theme implements a suggestion override.

Issue #761608 by JohnAlbin: Fixed Missing theme settings values because list_themes() has inconsistent theme object data.

Issue #1371484 by catch, makara, ArtistConk: Fixed Private properties in abstract class DrupalCacheArray.

This reverts commit 9db1fddb.

- Patch #953336 by sun, pillarsdotnet, chx: contributed modules are not able to test theme-related functionality.

Nate Lampton authored Oct 30, 2011 and catch committed Nov 01, 2011

Issue #22336 by quicksketch, scor, boombatower, and rfay. Move all core Drupal files under a core subdirectory.