Make createOptDrawState return NULL if we would end up not drawing

BUG=skia:

Review URL: https://codereview.chromium.org/630063002
diff --git a/tests/GLProgramsTest.cpp b/tests/GLProgramsTest.cpp
index a0d6427..d8ce3fd 100644
--- a/tests/GLProgramsTest.cpp
+++ b/tests/GLProgramsTest.cpp
@@ -332,7 +332,9 @@
             return false;
         }
 
-        SkAutoTUnref<GrOptDrawState> optState(this->getDrawState().createOptState(*this->caps()));
+        SkAutoTUnref<GrOptDrawState> optState(GrOptDrawState::Create(this->getDrawState(),
+                                                                     *this->caps(),
+                                                                     drawType));
         SkAutoTUnref<GrGLProgram> program(GrGLProgram::Create(this,
                                                               *optState.get(),
                                                               pdesc,