Clean up dead clear() code in SkRecord.

This removes the SkRecords::Clear struct and everything that refers to it.
Notice there is nothing actually creating a Clear, which means this is all
dead code.

Now that all ops obey the clip, I don't think we need the weird
inflate-empty-to-epsilon hack for BBH queries.

BUG=skia:

Review URL: https://codereview.chromium.org/835813002
diff --git a/tests/PictureBBHTest.cpp b/tests/PictureBBHTest.cpp
index 562d9b5..ac16dbb 100644
--- a/tests/PictureBBHTest.cpp
+++ b/tests/PictureBBHTest.cpp
@@ -63,7 +63,7 @@
 };
 
 // Test to verify the playback of an empty picture
-// 
+//
 class DrawEmptyPictureBBHTest : public PictureBBHTestBase {
 public:
     DrawEmptyPictureBBHTest()
@@ -78,7 +78,7 @@
 //
 class EmptyClipPictureBBHTest : public PictureBBHTestBase {
 public:
-    EmptyClipPictureBBHTest() 
+    EmptyClipPictureBBHTest()
         : PictureBBHTestBase(2, 2, 3, 3) { }
 
     virtual void doTest(SkCanvas& playbackCanvas, SkCanvas& recordingCanvas) SK_OVERRIDE {
@@ -101,35 +101,3 @@
     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);
-    SkAutoTUnref<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);
-    SkAutoTUnref<SkPicture> dstPic(dst.endRecording());
-
-    // Should be Clip - Save - Clear - Restore.
-    // Buggy implementations might return 1 (just Clip) or 3 (Clip - Save - Restore).
-    // TODO: can we just search that it contains "clear"? <reed>
-    REPORTER_ASSERT(r, dstPic->approximateOpCount() == 4 || dstPic->approximateOpCount() == 2);
-}
-
-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);
-}