Some files were using Blockly.utils.object.inherits (or .mixin) without
having imported Blockly.utils.object.
Similarly, trashcan.js tried to use utils.Size as a constructor
instead of importing Size from Blockly.utils.Size.
* Migrate core/events/events.js to ES6 const/let
* Migrate core/events/events.js to goog.module
* Migrate core/events/events.js to named requires
* clang-format core/events/events.js
* Migrate Blockly core to use getRecordUndo/setRecordUndo
* Update core/events.js to reflect latest guidance around exporting mutable fields
* Split provides in core/renderers/measurables/row_elements.js into individual files
* Migrate core/renderers/measurables/row_elements.js to ES6 const/let
* Migrate core/renderers/measurables/row_elements.js to goog.module
* Migrate core/renderers/measurables/row_elements.js to named requires
* clang-format core/renderers/measurables/row_elements.js
* Migrate core/widgetdiv.js to ES6 const/let
* Migrate core/widgetdiv.js to goog.module
* Migrate core/widgetdiv.js to named requires
* clang-format core/widgetdiv.js
* Mark WidgetDiv.DIV as deprecated and refactor callers to use setters/getters
* Fix deprecation date
* Refactor tests to make setDiv() in core/widgetdiv.js test-only
* Fix type annotations for WidgetDiv.DIV and move test cleanup into sharedTestTeardown
* Migrate core/renderers/minimalist/info.js to goog.module
* Migrate core/renderers/minimalist/info.js to named requires
* clang-format core/renderers/minimalist/info.js
* Migrate core/renderers/minimalist/constants.js to goog.module
* Migrate core/renderers/minimalist/constants.js to named requires
* clang-format core/renderers/minimalist/constants.js
* Migrate core/renderers/minimalist/renderer.js to goog.module
* Migrate core/renderers/minimalist/renderer.js to named requires
* clang-format core/renderers/minimalist/renderer.js
* Migrate core/utils/string.js to ES6 const/let
* Migrate core/utils/string.js to goog.module
* clang-format core/utils/string.js
* Migrate core/utils/string.js to current exports convention
* Convert two remaining vars to lets in core/utils/string.js
* Migrate core/variables.js to ES6 const/let
* Migrate core/variables.js to goog.module
* Migrate core/variables.js to named requires
* clang-format core/variables.js
* Add JSDoc and make testdeps function test-only
* Fix return type for getTestDeps
* Migrate to new style of exposing methods for mocking in core/variables.js
* Migrate core/procedures.js to ES6 const/let
* Migrate core/procedures.js to goog.module
* Migrate core/procedures.js to named requires
* clang-format core/procedures.js
* Rename xml to utilsXml to disambiguate from Xml
