fixed SkDrawCommand JSON generation
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1715443002

Review URL: https://codereview.chromium.org/1715443002
diff --git a/tools/debugger/SkDrawCommand.cpp b/tools/debugger/SkDrawCommand.cpp
index 674a359..b46e492 100644
--- a/tools/debugger/SkDrawCommand.cpp
+++ b/tools/debugger/SkDrawCommand.cpp
@@ -227,8 +227,7 @@
 
 Json::Value SkDrawCommand::drawToAndCollectJSON(SkCanvas* canvas,
                                                 UrlDataManager& urlDataManager) const {
-    Json::Value result;
-    result[SKDEBUGCANVAS_ATTRIBUTE_COMMAND] = this->GetCommandString(fOpType);
+    Json::Value result = this->toJSON(urlDataManager);
 
     SkASSERT(canvas);