Correctly set the viewport in layers.

Bug #2919295

Change-Id: I16ce79ab0d5747cb01c6c1abe531da3dfd93fb54
diff --git a/libs/hwui/Snapshot.h b/libs/hwui/Snapshot.h
index 9495bee..21b2bef 100644
--- a/libs/hwui/Snapshot.h
+++ b/libs/hwui/Snapshot.h
@@ -57,7 +57,8 @@
             flags(0),
             previous(s),
             layer(NULL),
-            fbo(s->fbo) {
+            fbo(s->fbo),
+            viewport(s->viewport) {
         if ((s->flags & Snapshot::kFlagClipSet) &&
                 !(s->flags & Snapshot::kFlagDirtyLocalClip)) {
             localClip.set(s->localClip);
@@ -180,6 +181,11 @@
     GLuint fbo;
 
     /**
+     * Current viewport.
+     */
+    Rect viewport;
+
+    /**
      * Contains the previous ortho matrix.
      */
     mat4 orthoMatrix;