Remove confusing behavior of Rect::intersect() and rename

bug:24670525

Removes silly 'do nothing if rects do not intersect' behavior, and
changes the name to clarify the difference (contrasting against
SkRect::intersect())

bug:24670525

Change-Id: Id2ca1cfea1a9d720d4dc70b251f426d9916f8b53
diff --git a/libs/hwui/renderthread/CanvasContext.cpp b/libs/hwui/renderthread/CanvasContext.cpp
index ddfd621..38f6e53 100644
--- a/libs/hwui/renderthread/CanvasContext.cpp
+++ b/libs/hwui/renderthread/CanvasContext.cpp
@@ -339,7 +339,7 @@
             // Remember the intersection of the target bounds and the intersection bounds against
             // which we have to crop the content.
             backdropBounds.set(x, y, x + backdropBounds.getWidth(), y + backdropBounds.getHeight());
-            backdropBounds.intersect(targetBounds);
+            backdropBounds.doIntersect(targetBounds);
             // Check if we have to draw something on the left side ...
             if (targetBounds.left < contentBounds.left) {
                 mCanvas->save(SkCanvas::kClip_SaveFlag);