add runtime option to provide data->imagegenerator factory

src/core/SkImageGenerator.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageGenerator.h"
 
 bool SkImageGenerator::getPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
@@ skipping 112 matching lines @@
                                                        size_t rb, const Options& options,
                                                        SkPMColor* colors, int* colorCount) {
     return kUnimplemented;
 }
 #else
 bool SkImageGenerator::onGetPixels(const SkImageInfo& info, void* dst, size_t rb,
                                    SkPMColor* colors, int* colorCount) {
     return false;
 }
 #endif
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+#include "SkGraphics.h"
+
+static SkGraphics::ImageGeneratorFromEncodedFactory gImageGeneratorFromEncodedFactory;
+
+SkGraphics::ImageGeneratorFromEncodedFactory SkGraphics::GetImageGeneratorFromEncodedFactory() {
+    return gImageGeneratorFromEncodedFactory;
+}
+
+void SkGraphics::SetImageGeneratorFromEncodedFactory(ImageGeneratorFromEncodedFactory factory) {
+    gImageGeneratorFromEncodedFactory = factory;
+}
+
+SkImageGenerator* SkImageGenerator::NewFromEncoded(SkData* data) {
+    if (NULL == data) {
+        return NULL;
+    }
+    if (gImageGeneratorFromEncodedFactory) {
+        if (SkImageGenerator* generator = gImageGeneratorFromEncodedFactory(data)) {
+            return generator;
+        }
+    }
+    return SkImageGenerator::NewFromEncodedImpl(data);
+}