SkRecordDraw: don't bother clipping an empty clip down further

src/record/SkRecordDraw.cpp

 #include "SkRecordDraw.h"
 
 namespace {
 
 // This is an SkRecord visitor that will draw that SkRecord to an SkCanvas.
 class Draw : SkNoncopyable {
 public:
     explicit Draw(SkCanvas* canvas) : fCanvas(canvas), fIndex(0), fClipEmpty(false) {}
 
     unsigned index() const { return fIndex; }
@@ skipping 19 matching lines @@
     } else {
         fCanvas->pushCull(r.rect);
     }
 }
 
 // These commands might change the clip.
 #define CASE(T, call) \
     template <> void Draw::operator()(const SkRecords::T& r) { fCanvas->call; this->updateClip(); }
 CASE(Restore, restore());
 CASE(SaveLayer, saveLayer(r.bounds, r.paint, r.flags));
+#undef CASE
+
+// These certainly do change the clip,
+// but we can skip them if they're intersecting with a clip that's already empty.
+#define CASE(T, call)  template <> void Draw::operator()(const SkRecords::T& r) {                \
+    if (!(fClipEmpty && SkRegion::kIntersect_Op == r.op)) { fCanvas->call; this->updateClip(); } \
+}
 CASE(ClipPath, clipPath(r.path, r.op, r.doAA));
 CASE(ClipRRect, clipRRect(r.rrect, r.op, r.doAA));
 CASE(ClipRect, clipRect(r.rect, r.op, r.doAA));
 CASE(ClipRegion, clipRegion(r.region, r.op));
 #undef CASE
 
-// Commands which must run regardless of the clip.
+// Commands which must run regardless of the clip, but don't change it themselves.
 #define CASE(T, call) \
     template <> void Draw::operator()(const SkRecords::T& r) { fCanvas->call; }
 CASE(Save, save(r.flags));
 CASE(Clear, clear(r.color));
 CASE(PopCull, popCull());
 #undef CASE
 
 // Nothing fancy below here.  These commands respect and don't change the clip.
 #define CASE(T, call) \
     template <> void Draw::operator()(const SkRecords::T& r) { if (!fClipEmpty) fCanvas->call; }
@@ skipping 20 matching lines @@
                                 r.xmode.get(), r.indices, r.indexCount, r.paint));
 #undef CASE
 
 }  // namespace
 
 void SkRecordDraw(const SkRecord& record, SkCanvas* canvas) {
     for (Draw draw(canvas); draw.index() < record.count(); draw.next()) {
         record.visit(draw.index(), draw);
     }
 }