Trying to be consistent when members are allowed to be NULL

src/effects/SkRectShaderImageFilter.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRectShaderImageFilter.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkDevice.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 #include "SkShader.h"
 
 SkRectShaderImageFilter* SkRectShaderImageFilter::Create(SkShader* s, const SkRect& rect) {
     SkASSERT(s);
     uint32_t flags = CropRect::kHasAll_CropEdge;
     if (rect.width() == 0 || rect.height() == 0) {
         flags = 0x0;
     }
     CropRect cropRect(rect, flags);
-    return SkNEW_ARGS(SkRectShaderImageFilter, (s, &cropRect));
+    return s ? SkNEW_ARGS(SkRectShaderImageFilter, (s, &cropRect)) : NULL;
 }
 
 SkRectShaderImageFilter* SkRectShaderImageFilter::Create(SkShader* s, const CropRect* cropRect, uint32_t uniqueID) {
     SkASSERT(s);
-    return SkNEW_ARGS(SkRectShaderImageFilter, (s, cropRect, uniqueID));
+    return s ? SkNEW_ARGS(SkRectShaderImageFilter, (s, cropRect, uniqueID)) : NULL;
 }
 
 SkRectShaderImageFilter::SkRectShaderImageFilter(SkShader* s, const CropRect* cropRect,
                                                  uint32_t uniqueID)
   : INHERITED(0, NULL, cropRect, uniqueID)
-  , fShader(s) {
-    SkASSERT(s);
-    s->ref();
+  , fShader(SkRef(s)) {
 }
 
 #ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
 SkRectShaderImageFilter::SkRectShaderImageFilter(SkReadBuffer& buffer)
   : INHERITED(0, buffer) {
     fShader = buffer.readShader();
 }
 #endif
 
 SkFlattenable* SkRectShaderImageFilter::CreateProc(SkReadBuffer& buffer) {
     SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 0);
     SkAutoTUnref<SkShader> shader(buffer.readShader());
     return Create(shader.get(), &common.cropRect(), common.uniqueID());
 }
 
 void SkRectShaderImageFilter::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writeFlattenable(fShader);
 }
 
 SkRectShaderImageFilter::~SkRectShaderImageFilter() {
-    SkSafeUnref(fShader);
+    fShader->unref();
 }
 
 bool SkRectShaderImageFilter::onFilterImage(Proxy* proxy,
                                             const SkBitmap& source,
                                             const Context& ctx,
                                             SkBitmap* result,
                                             SkIPoint* offset) const {
     SkIRect bounds;
     if (!this->applyCropRect(ctx, source, SkIPoint::Make(0, 0), &bounds)) {
         return false;
     }
 
     SkAutoTUnref<SkBaseDevice> device(proxy->createDevice(bounds.width(),
                                                           bounds.height()));
     if (NULL == device.get()) {
         return false;
     }
     SkCanvas canvas(device.get());
 
     SkPaint paint;
     SkMatrix matrix(ctx.ctm());
     matrix.postTranslate(SkIntToScalar(-bounds.left()), SkIntToScalar(-bounds.top()));
-    paint.setShader(SkShader::CreateLocalMatrixShader(fShader, matrix))->unref();
+    SkSafeUnref(paint.setShader(SkShader::CreateLocalMatrixShader(fShader, matrix)));
 
     SkRect rect = SkRect::MakeWH(SkIntToScalar(bounds.width()), SkIntToScalar(bounds.height()));
     canvas.drawRect(rect, paint);
 
     *result = device.get()->accessBitmap(false);
     offset->fX = bounds.fLeft;
     offset->fY = bounds.fTop;
     return true;
 }