move program descriptor generation to flush

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/829e1b80b1020b17f2078020c990e079b70c077c

Review URL: https://codereview.chromium.org/777673003
diff --git a/src/gpu/GrTest.cpp b/src/gpu/GrTest.cpp
index 48f72a7..7038c10 100644
--- a/src/gpu/GrTest.cpp
+++ b/src/gpu/GrTest.cpp
@@ -140,7 +140,7 @@
         return false;
     }
 
-    bool flushGraphicsState(const GrOptDrawState&, DrawType) SK_OVERRIDE { return false; }
+    bool flushGraphicsState(const GrOptDrawState&) SK_OVERRIDE { return false; }
 
     void clearStencil(GrRenderTarget* target) SK_OVERRIDE  {}