Create an SkCodecImageGenerator

BUG=skia:

patch from issue 1396323007 at patchset 120001 (http://crrev.com/1396323007#ps120001)
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1487683004

Review URL: https://codereview.chromium.org/1487683004
diff --git a/gyp/core.gyp b/gyp/core.gyp
index 13b8217..f195802 100644
--- a/gyp/core.gyp
+++ b/gyp/core.gyp
@@ -18,6 +18,7 @@
 
       'include_dirs': [
         '../include/c',
+        '../include/codec',
         '../include/config',
         '../include/core',
         '../include/pathops',
diff --git a/gyp/core.gypi b/gyp/core.gypi
index 1ecaa3e..bedde3f 100644
--- a/gyp/core.gypi
+++ b/gyp/core.gypi
@@ -67,6 +67,7 @@
         '<(skia_src_path)/core/SkChecksum.cpp',
         '<(skia_src_path)/core/SkChunkAlloc.cpp',
         '<(skia_src_path)/core/SkClipStack.cpp',
+        '<(skia_src_path)/core/SkCodecImageGenerator.cpp',
         '<(skia_src_path)/core/SkColor.cpp',
         '<(skia_src_path)/core/SkColorFilter.cpp',
         '<(skia_src_path)/core/SkColorFilterShader.cpp',
diff --git a/src/core/SkCodecImageGenerator.cpp b/src/core/SkCodecImageGenerator.cpp
new file mode 100644
index 0000000..2fef381
--- /dev/null
+++ b/src/core/SkCodecImageGenerator.cpp
@@ -0,0 +1,46 @@
+/*
+ * 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 "SkCodecImageGenerator.h"
+
+SkImageGenerator* SkCodecImageGenerator::NewFromEncodedCodec(SkData* data) {
+    SkCodec* codec = SkCodec::NewFromData(data);
+    if (nullptr == codec) {
+        return nullptr;
+    }
+
+    return new SkCodecImageGenerator(codec, data);
+}
+
+SkCodecImageGenerator::SkCodecImageGenerator(SkCodec* codec, SkData* data)
+    : INHERITED(codec->getInfo())
+    , fCodec(codec)
+    , fData(SkRef(data))
+{}
+
+SkData* SkCodecImageGenerator::onRefEncodedData(SK_REFENCODEDDATA_CTXPARAM) {
+    return SkRef(fData.get());
+}
+
+bool SkCodecImageGenerator::onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+        SkPMColor ctable[], int* ctableCount) {
+
+    SkCodec::Result result = fCodec->getPixels(info, pixels, rowBytes, nullptr, ctable,
+            ctableCount);
+    switch (result) {
+        case SkCodec::kSuccess:
+        case SkCodec::kIncompleteInput:
+            return true;
+        default:
+            return false;
+    }
+}
+
+bool SkCodecImageGenerator::onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
+        SkYUVColorSpace* colorSpace) {
+    return false;
+}
diff --git a/src/core/SkCodecImageGenerator.h b/src/core/SkCodecImageGenerator.h
new file mode 100644
index 0000000..80eacb1
--- /dev/null
+++ b/src/core/SkCodecImageGenerator.h
@@ -0,0 +1,43 @@
+/*
+ * 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 "SkCodec.h"
+#include "SkData.h"
+#include "SkImageGenerator.h"
+
+class SkCodecImageGenerator : public SkImageGenerator {
+public:
+    /*
+     * If this data represents an encoded image that we know how to decode,
+     * return an SkCodecImageGenerator.  Otherwise return nullptr.
+     *
+     * Refs the data if an image generator can be returned.  Otherwise does
+     * not affect the data.
+     */
+    static SkImageGenerator* NewFromEncodedCodec(SkData* data);
+
+protected:
+    SkData* onRefEncodedData(SK_REFENCODEDDATA_CTXPARAM) override;
+
+    bool onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, SkPMColor ctable[],
+            int* ctableCount) override;
+
+    bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
+            SkYUVColorSpace* colorSpace) override;
+
+private:
+    /*
+     * Takes ownership of codec
+     * Refs the data
+     */
+    SkCodecImageGenerator(SkCodec* codec, SkData* data);
+
+    SkAutoTDelete<SkCodec> fCodec;
+    SkAutoTUnref<SkData> fData;
+
+    typedef SkImageGenerator INHERITED;
+};
diff --git a/tests/CodexTest.cpp b/tests/CodexTest.cpp
index 96d03c1..2768d57 100644
--- a/tests/CodexTest.cpp
+++ b/tests/CodexTest.cpp
@@ -9,6 +9,7 @@
 #include "SkAndroidCodec.h"
 #include "SkBitmap.h"
 #include "SkCodec.h"
+#include "SkCodecImageGenerator.h"
 #include "SkData.h"
 #include "SkImageDecoder.h"
 #include "SkMD5.h"
@@ -379,6 +380,18 @@
                 &scaledCodecDigest, &codecDigest);
     }
 
+    // Test SkCodecImageGenerator
+    if (!isIncomplete) {
+        SkAutoTDelete<SkStream> stream(resource(path));
+        SkAutoTUnref<SkData> fullData(SkData::NewFromStream(stream, stream->getLength()));
+        SkAutoTDelete<SkImageGenerator> gen(SkCodecImageGenerator::NewFromEncodedCodec(fullData));
+        SkBitmap bm;
+        bm.allocPixels(info);
+        SkAutoLockPixels autoLockPixels(bm);
+        REPORTER_ASSERT(r, gen->getPixels(info, bm.getPixels(), bm.rowBytes()));
+        compare_to_good_digest(r, codecDigest, bm);
+    }
+
     // If we've just tested incomplete decodes, let's run the same test again on full decodes.
     if (isIncomplete) {
         check(r, path, size, supportsScanlineDecoding, supportsSubsetDecoding, false);