DM: failure to canary a sink is now fatal.

dm/DM.cpp

Index: dm/DM.cpp
diff --git a/dm/DM.cpp b/dm/DM.cpp
index ff9dc572643f821c3e189d5771f4612cefbe9a59..c0fccaaa2c7bfcee54624fb32f02af5f4771161a 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -300,8 +300,8 @@ static void push_sink(const char* tag, Sink* s) {
     SkString log;
     Error err = sink->draw(noop, &bitmap, &stream, &log);
     if (err.isFatal()) {
-        SkDebugf("Skipping %s: %s\n", tag, err.c_str());
-        return;
+        SkDebugf("Could not run %s: %s\n", tag, err.c_str());
+        exit(1);
     }
 
     Tagged<Sink>& ts = gSinks.push_back();