Fix matrix mapping of negative rects

bug:27381362

Also rejects ops with empty clip at record time, and short circuits clip
intersection, when one is empty.

Change-Id: I842612da14ad8fd9f1ba5e9e4fd027ba4e08d365
diff --git a/libs/hwui/ClipArea.cpp b/libs/hwui/ClipArea.cpp
index e368537..501cbe5 100644
--- a/libs/hwui/ClipArea.cpp
+++ b/libs/hwui/ClipArea.cpp
@@ -404,11 +404,17 @@
     return currentRectCount + recordedRectCount > RectangleList::kMaxTransformedRectangles;
 }
 
+static const ClipRect sEmptyClipRect(Rect(0, 0));
+
 const ClipBase* ClipArea::serializeIntersectedClip(LinearAllocator& allocator,
         const ClipBase* recordedClip, const Matrix4& recordedClipTransform) {
+
     // if no recordedClip passed, just serialize current state
     if (!recordedClip) return serializeClip(allocator);
 
+    // if either is empty, clip is empty
+    if (CC_UNLIKELY(recordedClip->rect.isEmpty())|| mClipRect.isEmpty()) return &sEmptyClipRect;
+
     if (!mLastResolutionResult
             || recordedClip != mLastResolutionClip
             || recordedClipTransform != mLastResolutionTransform) {