Rename Caret.{h,cpp} to CaretBase to match class.

Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/EffectModel.idl',
             'animation/AnimationEffectReadOnly.idl',
@@ skipping 1252 matching lines @@
             'css/resolver/StyleResolverState.cpp',
             'css/resolver/StyleResolverState.h',
             'css/resolver/StyleResolverStats.cpp',
             'css/resolver/StyleResolverStats.h',
             'css/resolver/StyleResourceLoader.cpp',
             'css/resolver/StyleResourceLoader.h',
             'css/resolver/TransformBuilder.cpp',
             'css/resolver/TransformBuilder.h',
             'css/resolver/ViewportStyleResolver.cpp',
             'css/resolver/ViewportStyleResolver.h',
-            'editing/Caret.cpp',
-            'editing/Caret.h',
+            'editing/CaretBase.cpp',
+            'editing/CaretBase.h',
             'editing/CompositionUnderline.h',
             'editing/CompositionUnderlineRangeFilter.cpp',
             'editing/CompositionUnderlineRangeFilter.h',
             'editing/DOMSelection.cpp',
             'editing/DOMSelection.h',
             'editing/DragCaretController.cpp',
             'editing/DragCaretController.h',
             'editing/EditingBehavior.cpp',
             'editing/EditingBehavior.h',
             'editing/EditingStrategy.cpp',
@@ skipping 2562 matching lines @@
             'style/OutlineValueTest.cpp',
             'style/SVGComputedStyleTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }