Bug 856472: Move CanvasPattern to its own file r=bz

--HG--
rename : content/canvas/src/CanvasRenderingContext2D.h => content/canvas/src/CanvasPattern.h
Bug 856472: Convert CanvasPattern to WebIDL r=bz
Bug 856472: Wrappercache CanvasPattern r=bz
Bug 856472: Move CanvasGradient to its own file r=bz

--HG--
rename : content/canvas/src/CanvasRenderingContext2D.h => content/canvas/src/CanvasGradient.h
Bug 856472: Convert CanvasGradient to WebIDL r=bz
Bug 856472: Wrappercache CanvasGradient r=bz
Bug 856472: Fix includes and WrapObject r=me