Make sure pictures draw Clears even when the clip is empty.

tests/PictureBBHTest.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCanvas.h"
 #include "SkBBoxHierarchy.h"
 #include "SkPaint.h"
@@ skipping 31 matching lines @@
         // With an R-Tree
         SkRTreeFactory RTreeFactory;
         this->run(&RTreeFactory, reporter);
     }
 
 private:
     void run(SkBBHFactory* factory, skiatest::Reporter* reporter) {
         SkCanvas playbackCanvas(fResultBitmap);
         playbackCanvas.clear(SK_ColorGREEN);
         SkPictureRecorder recorder;
-        SkCanvas* recordCanvas = recorder.beginRecording(SkIntToScalar(fPictureWidth), SkIntToScalar(fPictureHeight), factory);
+        SkCanvas* recordCanvas = recorder.beginRecording(SkIntToScalar(fPictureWidth),
+                                                         SkIntToScalar(fPictureHeight),
+                                                         factory);
         this->doTest(playbackCanvas, *recordCanvas);
         SkAutoTUnref<SkPicture> picture(recorder.endRecording());
         playbackCanvas.drawPicture(picture);
         REPORTER_ASSERT(reporter, SK_ColorGREEN == fResultBitmap.getColor(0, 0));
     }
 
     SkBitmap fResultBitmap;
     int fPictureWidth, fPictureHeight;
 };
 
@@ skipping 29 matching lines @@
 };
 
 DEF_TEST(PictureBBH, reporter) {
 
     DrawEmptyPictureBBHTest emptyPictureTest;
     emptyPictureTest.run(reporter);
 
     EmptyClipPictureBBHTest emptyClipPictureTest;
     emptyClipPictureTest.run(reporter);
 }
+
+static void test_clear(skiatest::Reporter* r, SkBBHFactory* factory) {
+    // SkPicture should always call clear()s on the target canvas, even if its clip is empty.
+    SkPictureRecorder src, dst;
+
+    // A picture that's just clear().
+    src.beginRecording(1,1, factory)
+        ->clear(SK_ColorGREEN);
+    SkAutoTDelete<SkPicture> srcPic(src.endRecording());
+
+    // A target canvas with an empty clip.
+    SkCanvas* c = dst.beginRecording(1,1, NULL);
+        c->clipRect(SkRect::MakeEmpty());
+        srcPic->playback(c);
+    SkAutoTDelete<SkPicture> dstPic(dst.endRecording());
+
+    // Should be Clip - Save - Clear - Restore.
+    // Buggy implementations might return 1 (just Clip) or 3 (Clip - Save - Restore).
+    REPORTER_ASSERT(r, dstPic->approximateOpCount() == 4);
+}
+
+DEF_TEST(PictureBBH_Clear, r) {
+    test_clear(r, NULL);
+
+    SkTileGridFactory::TileGridInfo grid = { {1,1}, {0,0}, {0,0} };
+    SkTileGridFactory tilegrid(grid);
+    test_clear(r, &tilegrid);
+
+    SkRTreeFactory rtree;
+    test_clear(r, &rtree);
+}