Refactor ImageBuffer to make OffscreenCanvas match HTMLCanvasElement

third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.idl

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // https://html.spec.whatwg.org/multipage/scripting.html#the-offscreen-2d-rendering-context
 
 [
     Exposed=(Window,Worker),
     RuntimeEnabled=ExperimentalCanvasFeatures,
 ] interface OffscreenCanvasRenderingContext2D {
@@ skipping 58 matching lines @@
     [CallWith=ScriptState, RaisesException] void drawImage(CanvasImageSource image, unrestricted double x, unrestricted double y);
     [CallWith=ScriptState, RaisesException] void drawImage(CanvasImageSource image, unrestricted double x, unrestricted double y, unrestricted double width, unrestricted double height);
     [CallWith=ScriptState, RaisesException] void drawImage(CanvasImageSource image, unrestricted double sx, unrestricted double sy, unrestricted double sw, unrestricted double sh, unrestricted double dx, unrestricted double dy, unrestricted double dw, unrestricted double dh);
 
     // pixel manipulation
     [RaisesException] ImageData createImageData(ImageData imagedata);
     [RaisesException] ImageData createImageData(long sw, long sh);
     [RaisesException] ImageData getImageData(long sx, long sy, long sw, long sh);
     [RaisesException] void putImageData(ImageData imagedata, long dx, long dy);
     [RaisesException] void putImageData(ImageData imagedata, long dx, long dy, long dirtyX, long dirtyY, long dirtyWidth, long dirtyHeight);
- 
+
     // If OffscreenCanva ships before color managed canvas, this method must remain behind flag.
     // https://github.com/WICG/canvas-color-space/blob/master/CanvasColorSpaceProposal.md
     [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] ImageData createImageData(unsigned long sw, unsigned long sh, ImageDataColorSettings imageDataColorSettings);
     [RuntimeEnabled=ExperimentalCanvasFeatures, RaisesException] ImageData createImageData(ImageDataArray data, unsigned long sw, unsigned long sh, ImageDataColorSettings imageDataColorSettings);
 
 
     // Line caps/joins
     attribute unrestricted double lineWidth; // (default 1)
     attribute DOMString lineCap; // "butt", "round", "square" (default "butt")
     attribute DOMString lineJoin; // "round", "bevel", "miter" (default "miter")
     attribute unrestricted double miterLimit; // (default 10)
 
     // dashed lines
     void setLineDash(sequence<unrestricted double> dash);
     sequence<unrestricted double> getLineDash();
     attribute unrestricted double lineDashOffset;
 };
 
 OffscreenCanvasRenderingContext2D implements CanvasPath;