lots of sRGB and F16 blits

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 653f4b117f4fa45b6a475a618a1e1337b0e47c36..9cb24c13645d321904f7a8a12927a4aa2d18a15a 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -1167,6 +1167,17 @@ static void draw_filter_into_device(SkBaseDevice* src, const SkImageFilter* filt
     c.drawBitmap(srcBM, x, y, &p);
 }
 
+static SkImageInfo make_layer_info(const SkImageInfo& prev, int w, int h, bool isOpaque) {
+    SkAlphaType alphaType = isOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType;
+    if (prev.bytesPerPixel() < 4) {
+        // promote to 32bits
+        return SkImageInfo::MakeN32(w, h, alphaType);
+    } else {
+        // keep the same characteristics as the prev
+        return SkImageInfo::Make(w, h, prev.colorType(), alphaType, prev.profileType());
+    }
+}
+
 void SkCanvas::internalSaveLayer(const SaveLayerRec& rec, SaveLayerStrategy strategy) {
     const SkRect* bounds = rec.fBounds;
     const SkPaint* paint = rec.fPaint;
@@ -1202,8 +1213,6 @@ void SkCanvas::internalSaveLayer(const SaveLayerRec& rec, SaveLayerStrategy stra
             geo = kUnknown_SkPixelGeometry;
         }
     }
-    SkImageInfo info = SkImageInfo::MakeN32(ir.width(), ir.height(),
-                        isOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
 
     SkBaseDevice* device = this->getTopDevice();
     if (nullptr == device) {
@@ -1211,6 +1220,8 @@ void SkCanvas::internalSaveLayer(const SaveLayerRec& rec, SaveLayerStrategy stra
         return;
     }
 
+    SkImageInfo info = make_layer_info(device->imageInfo(), ir.width(), ir.height(), isOpaque);
+
     bool forceSpriteOnRestore = false;
     {
         const bool preserveLCDText = kOpaque_SkAlphaType == info.alphaType() ||