change SkStreams to work with sk_sp<SkData> instead of SkData*

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2333713002

Review-Url: https://codereview.chromium.org/2333713002
diff --git a/tools/skiaserve/Request.cpp b/tools/skiaserve/Request.cpp
index 22fa211..ea2d17a 100644
--- a/tools/skiaserve/Request.cpp
+++ b/tools/skiaserve/Request.cpp
@@ -65,7 +65,7 @@
     SkDynamicMemoryWStream buffer;
     SkDrawCommand::WritePNG((const png_bytep) encodedBitmap->bytes(), bmp->width(), bmp->height(),
                             buffer, true);
-    return sk_sp<SkData>(buffer.copyToData());
+    return buffer.detachAsData();
 }
 
 SkCanvas* Request::getCanvas() {
@@ -117,7 +117,7 @@
     SkAutoTUnref<SkPixelSerializer> serializer(SkImageEncoder::CreatePixelSerializer());
     picture->serialize(&outStream, serializer);
 
-    return sk_sp<SkData>(outStream.copyToData());
+    return outStream.detachAsData();
 }
 
 GrContext* Request::getContext() {
@@ -257,7 +257,7 @@
     SkDynamicMemoryWStream stream;
     stream.writeText(Json::FastWriter().write(root).c_str());
 
-    return sk_sp<SkData>(stream.copyToData());
+    return stream.detachAsData();
 }
 
 sk_sp<SkData> Request::getJsonBatchList(int n) {
@@ -269,7 +269,7 @@
     SkDynamicMemoryWStream stream;
     stream.writeText(Json::FastWriter().write(result).c_str());
 
-    return sk_sp<SkData>(stream.copyToData());
+    return stream.detachAsData();
 }
 
 sk_sp<SkData> Request::getJsonInfo(int n) {
@@ -301,7 +301,7 @@
 
     // Convert to format suitable for inspection
     sk_sp<SkData> encodedBitmap = sk_tools::encode_bitmap_for_png(*bitmap);
-    SkASSERT(encodedBitmap.get());
+    SkASSERT(encodedBitmap);
 
     const uint8_t* start = encodedBitmap->bytes() + ((y * bitmap->width() + x) * 4);
     SkColor result = SkColorSetARGB(start[3], start[0], start[1], start[2]);