Add SkSpecialImage::extractSubset & NewFromPixmap

src/core/SkAutoPixmapStorage.cpp

Index: src/core/SkAutoPixmapStorage.cpp
diff --git a/src/core/SkAutoPixmapStorage.cpp b/src/core/SkAutoPixmapStorage.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..3be28a94c428984a7a5665fed1e76f19890b855b
--- /dev/null
+++ b/src/core/SkAutoPixmapStorage.cpp
@@ -0,0 +1,64 @@
+
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkAutoPixmapStorage.h"
+#include "SkData.h"
+
+SkAutoPixmapStorage::SkAutoPixmapStorage() : fStorage(nullptr) {}
+
+SkAutoPixmapStorage::~SkAutoPixmapStorage() {
+    this->freeStorage();
+}
+
+size_t SkAutoPixmapStorage::AllocSize(const SkImageInfo& info, size_t* rowBytes) {
+    size_t rb = info.minRowBytes();
+    if (rowBytes) {
+        *rowBytes = rb;
+    }
+    return info.getSafeSize(rb);
+}
+
+bool SkAutoPixmapStorage::tryAlloc(const SkImageInfo& info) {
+    this->freeStorage();
+
+    size_t rb;
+    size_t size = AllocSize(info, &rb);
+    if (0 == size) {
+        return false;
+    }
+    void* pixels = sk_malloc_flags(size, 0);
+    if (nullptr == pixels) {
+        return false;
+    }
+    this->reset(info, pixels, rb);
+    fStorage = pixels;
+    return true;
+}
+
+void SkAutoPixmapStorage::alloc(const SkImageInfo& info) {
+    if (!this->tryAlloc(info)) {
+        sk_throw();
+    }
+}
+
+const SkData* SkAutoPixmapStorage::detachPixelsAsData() {
+    if (!fStorage) {
+        return nullptr;
+    }
+
+    auto data = SkData::MakeFromMalloc(fStorage, this->getSafeSize());
+    fStorage = nullptr;
+    this->INHERITED::reset();
+
+    return data.release();
+}
+
+void SkAutoPixmapStorage::release() {
+    fStorage = nullptr;
+    this->INHERITED::reset();
+}