API to support native scaling by image-generator

src/core/SkImageGenerator.cpp

Index: src/core/SkImageGenerator.cpp
diff --git a/src/core/SkImageGenerator.cpp b/src/core/SkImageGenerator.cpp
index 5e401920cd97a68cf5cb5e88e73a3fa9d6092c99..dcd3ad00b17e812d27b647360b9f4529463124f5 100644
--- a/src/core/SkImageGenerator.cpp
+++ b/src/core/SkImageGenerator.cpp
@@ -111,6 +111,30 @@ GrTexture* SkImageGenerator::generateTexture(GrContext* ctx, const SkIRect* subs
     return this->onGenerateTexture(ctx, subset);
 }
 
+bool SkImageGenerator::computeScaledDimensions(SkScalar scale, SupportedSizes* sizes) {
+    if (scale > 0 && scale <= 1) {
+        return this->onComputeScaledDimensions(scale, sizes);
+    }
+    return false;
+}
+
+bool SkImageGenerator::generateScaledPixels(const SkISize& scaledSize,
+                                            const SkIPoint& subsetOrigin,
+                                            const SkPixmap& subsetPixels) {
+    if (scaledSize.width() <= 0 || scaledSize.height() <= 0) {
+        return false;
+    }
+    if (subsetPixels.width() <= 0 || subsetPixels.height() <= 0) {
+        return false;
+    }
+    const SkIRect subset = SkIRect::MakeXYWH(subsetOrigin.x(), subsetOrigin.y(),
+                                             subsetPixels.width(), subsetPixels.height());
+    if (!SkIRect::MakeWH(scaledSize.width(), scaledSize.height()).contains(subset)) {
+        return false;
+    }
+    return this->onGenerateScaledPixels(scaledSize, subsetOrigin, subsetPixels);
+}
+
 /////////////////////////////////////////////////////////////////////////////////////////////
 
 SkData* SkImageGenerator::onRefEncodedData() {