dm: log log

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1771993002

Review URL: https://codereview.chromium.org/1771993002
diff --git a/dm/DM.cpp b/dm/DM.cpp
index f2c74e307..6830cee 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -987,6 +987,13 @@
             start(task.sink.tag.c_str(), task.src.tag.c_str(),
                   task.src.options.c_str(), name.c_str());
             Error err = task.sink->draw(*task.src, &bitmap, &stream, &log);
+            if (!log.isEmpty()) {
+                SkDebugf("%s %s %s %s:\n%s\n", task.sink.tag.c_str()
+                                             , task.src.tag.c_str()
+                                             , task.src.options.c_str()
+                                             , name.c_str()
+                                             , log.c_str());
+            }
             if (!err.isEmpty()) {
                 if (err.isFatal()) {
                     fail(SkStringPrintf("%s %s %s %s: %s",