Remove support for -webkit-canvas and Document.getCSSCanvasContext.

third_party/WebKit/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 1018 matching lines @@
             'css/BasicShapeFunctions.cpp',
             'css/BinaryDataFontFaceSource.cpp',
             'css/BinaryDataFontFaceSource.h',
             'css/CSSBasicShapeValues.cpp',
             'css/CSSBorderImage.cpp',
             'css/CSSBorderImage.h',
             'css/CSSBorderImageSliceValue.cpp',
             'css/CSSBorderImageSliceValue.h',
             'css/CSSCalculationValue.cpp',
             'css/CSSCalculationValue.h',
-            'css/CSSCanvasValue.cpp',
-            'css/CSSCanvasValue.h',
             'css/CSSColorValue.h',
             'css/CSSComputedStyleDeclaration.cpp',
             'css/CSSContentDistributionValue.cpp',
             'css/CSSContentDistributionValue.h',
             'css/CSSCounterValue.cpp',
             'css/CSSCounterValue.h',
             'css/CSSCrossfadeValue.cpp',
             'css/CSSCrossfadeValue.h',
             'css/CSSCursorImageValue.cpp',
             'css/CSSCustomFontData.h',
@@ skipping 2884 matching lines @@
             'style/SVGComputedStyleTest.cpp',
             'svg/SVGPathParserTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }