Fix flushing of context in ViaDDL

Change-Id: I9f84f4081861e2789b45787405e0f1a5aa87824d
Reviewed-on: https://skia-review.googlesource.com/116546
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 4e1e31d..8650a5d 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -2669,6 +2669,7 @@
                     // DDL TODO: remove the cleanUpVRAM method and use the release & done
                     // callbacks.
                     GrGpu* gpu = context->contextPriv().getGpu();
+                    context->flush();
                     gpu->testingOnly_flushGpuAndSync();
 
                     helper.cleanUpVRAM(context);