SkPaintFilterCanvas should inherit the target canvas state

src/utils/SkPaintFilterCanvas.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPaintFilterCanvas.h"
 
 #include "SkPaint.h"
@@ skipping 12 matching lines @@
     }
 
     const SkPaint* paint() const { return fLazyPaint.getMaybeNull(); }
 
 private:
     SkTLazy<SkPaint> fLazyPaint;
 };
 
 SkPaintFilterCanvas::SkPaintFilterCanvas(int width, int height) : INHERITED(width, height) { }
 
+SkPaintFilterCanvas::SkPaintFilterCanvas(SkCanvas *canvas)
+    : INHERITED(canvas->imageInfo().width(), canvas->imageInfo().height()) {
+
+    // Transfer matrix & clip state before adding the target canvas.
+    SkIRect devClip;
+    canvas->getClipDeviceBounds(&devClip);
+    this->clipRect(SkRect::Make(devClip));
+    this->setMatrix(canvas->getTotalMatrix());
+
+    this->addCanvas(canvas);
+}
+
 void SkPaintFilterCanvas::onDrawPaint(const SkPaint& paint) {
     AutoPaintFilter apf(this, kPaint_Type, paint);
     this->INHERITED::onDrawPaint(*apf.paint());
 }
 
 void SkPaintFilterCanvas::onDrawPoints(PointMode mode, size_t count, const SkPoint pts[],
                                        const SkPaint& paint) {
     AutoPaintFilter apf(this, kPoint_Type, paint);
     this->INHERITED::onDrawPoints(mode, count, pts, *apf.paint());
 }
@@ skipping 106 matching lines @@
                                            const SkMatrix* matrix, const SkPaint& paint) {
     AutoPaintFilter apf(this, kText_Type, paint);
     this->INHERITED::onDrawTextOnPath(text, byteLength, path, matrix, *apf.paint());
 }
 
 void SkPaintFilterCanvas::onDrawTextBlob(const SkTextBlob* blob, SkScalar x, SkScalar y,
                                          const SkPaint& paint) {
     AutoPaintFilter apf(this, kTextBlob_Type, paint);
     this->INHERITED::onDrawTextBlob(blob, x, y, *apf.paint());
 }