change canvas-state to just record clip bounds

This reflects the long-standing restrictions in our clients (webview) and the reality of the gpu target which just uses scissors.

It also removes one of the few callers of canvas::clipRegion, which we'd like to remove.

Bug: skia:
Change-Id: Ie3b3c6e8752f82cddef256f753000f9da4bdbdee
Reviewed-on: https://skia-review.googlesource.com/113260
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 24a6d4a..4eb735e 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -2797,8 +2797,8 @@
     return *paint;
 }
 
-void SkCanvas::LayerIter::clip(SkRegion* rgn) const {
-    return fImpl->fDevice->onAsRgnClip(rgn);
+SkIRect SkCanvas::LayerIter::clipBounds() const {
+    return fImpl->fDevice->getGlobalBounds();
 }
 
 int SkCanvas::LayerIter::x() const { return fImpl->getX(); }