9 files declare their use of ContextAwarePluginBase in Drupal 8

BlockBase.php in core/lib/Drupal/Core/Block/BlockBase.php

ContextAwarePluginBaseTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Context/ContextAwarePluginBaseTest.php

ContextHandlerTest.php in core/tests/Drupal/KernelTests/Core/Plugin/ContextHandlerTest.php

ExecutablePluginBase.php in core/lib/Drupal/Core/Executable/ExecutablePluginBase.php

MockComplexContextBlock.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/mock_block/MockComplexContextBlock.php

MockUserNameBlock.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/mock_block/MockUserNameBlock.php

SectionStorageBase.php in core/modules/layout_builder/src/Plugin/SectionStorage/SectionStorageBase.php

SimpleConfigSectionStorage.php in core/modules/layout_builder/tests/modules/layout_builder_test/src/Plugin/SectionStorage/SimpleConfigSectionStorage.php

TypedDataStringBlock.php in core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/mock_block/TypedDataStringBlock.php