Correct viewport initialization, bounds comparison

Change-Id: Ibd751856e3712991e149800ed179464397dad7c3
diff --git a/libs/hwui/OpenGLRenderer.cpp b/libs/hwui/OpenGLRenderer.cpp
index 4df97e6..921c77b 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -662,7 +662,9 @@
         // When the layer is not an FBO, we may use glCopyTexImage so we
         // need to make sure the layer does not extend outside the bounds
         // of the framebuffer
-        if (!bounds.intersect(Rect(0, 0, getViewportWidth(), getViewportHeight()))) {
+        const Snapshot& previous = *(currentSnapshot()->previous);
+        Rect previousViewport(0, 0, previous.getViewportWidth(), previous.getViewportHeight());
+        if (!bounds.intersect(previousViewport)) {
             bounds.setEmpty();
         } else if (fboLayer) {
             clip.set(bounds);