Pull up a subset of CanvasRenderingContext2D into BaseRenderingContext2D.

third_party/WebKit/Source/modules/modules.gypi

 {
   'includes': [
     '../core/core_generated.gypi',
     'modules_generated.gypi',
   ],
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
@@ skipping 812 matching lines @@
       'cachestorage/Cache.cpp',
       'cachestorage/Cache.h',
       'cachestorage/CacheStorage.cpp',
       'cachestorage/CacheStorage.h',
       'cachestorage/CacheStorageError.cpp',
       'cachestorage/CacheStorageError.h',
       'cachestorage/GlobalCacheStorage.cpp',
       'cachestorage/GlobalCacheStorage.h',
       'cachestorage/InspectorCacheStorageAgent.cpp',
       'cachestorage/InspectorCacheStorageAgent.h',
+      'canvas2d/BaseRenderingContext2D.cpp',
+      'canvas2d/BaseRenderingContext2D.h',
       'canvas2d/CanvasGradient.cpp',
       'canvas2d/CanvasGradient.h',
       'canvas2d/CanvasPathMethods.cpp',
       'canvas2d/CanvasPathMethods.h',
       'canvas2d/CanvasPattern.cpp',
       'canvas2d/CanvasPattern.h',
       'canvas2d/CanvasRenderingContext2D.cpp',
       'canvas2d/CanvasRenderingContext2D.h',
       'canvas2d/CanvasRenderingContext2DState.cpp',
       'canvas2d/CanvasRenderingContext2DState.h',
@@ skipping 1086 matching lines @@
       'webaudio/AudioBasicProcessorHandlerTest.cpp',
       'webaudio/ConvolverNodeTest.cpp',
       'webaudio/DynamicsCompressorNodeTest.cpp',
       'webaudio/ScriptProcessorNodeTest.cpp',
       'webaudio/StereoPannerNodeTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/DocumentWebSocketChannelTest.cpp',
     ],
   },
 }