Fix missing first frame

Bug: 26776366
Change-Id: I46258c0ff35fdefe5c9f2ee610c904b2dbe8c5d9
diff --git a/libs/hwui/Layer.h b/libs/hwui/Layer.h
index e00ae66..1e5498b 100644
--- a/libs/hwui/Layer.h
+++ b/libs/hwui/Layer.h
@@ -216,6 +216,10 @@
         this->renderTarget = renderTarget;
     }
 
+    inline bool isRenderable() const {
+        return renderTarget != GL_NONE;
+    }
+
     void setWrap(GLenum wrap, bool bindTexture = false, bool force = false) {
         texture.setWrap(wrap, bindTexture, force, renderTarget);
     }