Avoid re-rendering stencil clip for every draw with reducable clip stack

src/gpu/GrStencilBuffer.h

Index: src/gpu/GrStencilBuffer.h
diff --git a/src/gpu/GrStencilBuffer.h b/src/gpu/GrStencilBuffer.h
index 3765a4c657074768142c0066da562350d77d5acd..37d40f16ba73544e6371c4e6f23ed4dd040de343 100644
--- a/src/gpu/GrStencilBuffer.h
+++ b/src/gpu/GrStencilBuffer.h
@@ -43,8 +43,7 @@ public:
     bool mustRenderClip(int32_t clipStackGenID,
                         const SkIRect& clipSpaceRect,
                         const SkIPoint clipSpaceToStencilOffset) const {
-        return SkClipStack::kInvalidGenID == clipStackGenID ||
-               fLastClipStackGenID != clipStackGenID ||
+        return fLastClipStackGenID != clipStackGenID ||
                fLastClipSpaceOffset != clipSpaceToStencilOffset ||
                !fLastClipStackRect.contains(clipSpaceRect);
     }