[sksg] Refine invalidation logic

We need to discriminate between nodes whose bounds updates contribute to the dirty
region, and nodes whose bounds changes do not.

E.g. animated shape in a group: the animated shape node bounds should yield damage,
but the ancestor group bounds should not.

To accomplish this, we refine the invalidation state:

  1) self invalidation == the node itself was invalidated, and its bounds updates
     yield damage.
  2) descendant invalidation == the node has some (self-)invalidated descendant,
     but its own bounds are not contributing damage.

Also:

  * hoist the bounding box invalidation logic into the base class (Node::revalidate)
    and update to respect the states described above.
  * remove (now-redundant) GeometryNode bbox logic.
  * update revalidation methods to return the node bbox instead of void

TBR=
Change-Id: I8023d1793fb501c945a53f2dc2d2983e5b620ade
Reviewed-on: https://skia-review.googlesource.com/90581
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/experimental/sksg/SkSGInvalidationController.cpp b/experimental/sksg/SkSGInvalidationController.cpp
index 4b133d8..81a3376 100644
--- a/experimental/sksg/SkSGInvalidationController.cpp
+++ b/experimental/sksg/SkSGInvalidationController.cpp
@@ -12,9 +12,13 @@
 
 namespace sksg {
 
-InvalidationController::InvalidationController() {}
+InvalidationController::InvalidationController() : fBounds(SkRect::MakeEmpty()) {}
 
 void InvalidationController::inval(const SkRect& r, const SkMatrix& ctm) {
+    if (r.isEmpty()) {
+        return;
+    }
+
     SkTCopyOnFirstWrite<SkRect> rect(r);
 
     if (!ctm.isIdentity()) {
@@ -22,6 +26,7 @@
     }
 
     fRects.push(*rect);
+    fBounds.join(*rect);
 }
 
 } // namespace sksg