Break up SkLazyPixelRef functionally into class hierarchy.

src/lazy/SkLazyCachingPixelRef.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 "Sk64.h"
+#include "SkColorTable.h"
+#include "SkData.h"
+#include "SkImageDecoder.h"
+#include "SkImagePriv.h"
+#include "SkLazyCachingPixelRef.h"
+#include "SkPostConfig.h"
+#include "SkScaledImageCache.h"
+
+SkLazyCachingPixelRef::SkLazyCachingPixelRef(SkData* data,
+                                             SkBitmapFactory::DecodeProc proc,
+                                             SkScaledImageCache* cache)
+    : INHERITED(cache)
+    , fDecodeProc(proc) {
+    if (NULL == data) {
+        fData = SkData::NewEmpty();
+    } else {
+        fData = data;
+        fData->ref();
+    }
+    if (NULL == fDecodeProc) {  // use a reasonable default.
+        fDecodeProc = SkImageDecoder::DecodeMemoryToTarget;
+    }
+    this->setImmutable();
+}
+
+SkLazyCachingPixelRef::~SkLazyCachingPixelRef() {
+    SkASSERT(fData != NULL);
+    fData->unref();
+}
+
+bool SkLazyCachingPixelRef::onDecodeInfo(SkImageInfo* info) {
+    SkASSERT(info);
+    return fDecodeProc(fData->data(), fData->size(), info, NULL);
+}
+
+bool SkLazyCachingPixelRef::onDecode(void* pixels, size_t rowBytes) {
+    SkASSERT(pixels);
+    SkImageInfo info = this->getInfo();  // local copy of info.

[scroggo, 2013/11/01 18:27:55]

Shouldn't this be const SkImageInfo& info, as it is currently written?

I kind of like the model where getInfo() returns a pointer though, so instead of
checking fWidth, down below, we can just compare against NULL.

[hal.canary, 2013/11/01 18:52:59]

DecodeProc takes a non-const info, so I have to copy it.  This is a quirk of
that function.
That's not a bad idea.

+    if (info.fWidth < 0) {  // getInfo() failed
+        return false;
+    }
+    SkBitmapFactory::Target target = {pixels, rowBytes};
+    return fDecodeProc(fData->data(), fData->size(), &info, &target);
+}
+
+bool SkLazyCachingPixelRef::Install(SkBitmapFactory::DecodeProc proc,
+                                    SkData* data,
+                                    SkBitmap* destination,
+                                    SkScaledImageCache* cache) {
+    SkAutoTUnref<SkLazyCachingPixelRef> ref(
+        SkNEW_ARGS(SkLazyCachingPixelRef, (data, proc, cache)));
+    return ref->configure(destination) && destination->setPixelRef(ref);
+}
+