Flush the pipe in skiaserve when we switch to GPU

tools/skiaserve/Request.cpp

Index: tools/skiaserve/Request.cpp
diff --git a/tools/skiaserve/Request.cpp b/tools/skiaserve/Request.cpp
index a0580754107667994ee4d12b03a8521a4d7a6ccb..61f0e1041cd97683114f065ffe06dc65d0afea16 100644
--- a/tools/skiaserve/Request.cpp
+++ b/tools/skiaserve/Request.cpp
@@ -177,6 +177,13 @@ bool Request::enableGPU(bool enable) {
         if (surface) {
             fSurface.reset(surface);
             fGPUEnabled = true;
+
+            // When we switch to GPU, there seems to be some mystery draws in the canvas.  So we
+            // draw once to flush the pipe
+            // TODO understand what is actually happening here
+            fDebugCanvas->drawTo(this->getCanvas(), this->getLastOp());
+            this->getCanvas()->flush();
+
             return true;
         }
         return false;