tell our grcontext to abandon its backend

samplecode/SampleApp.cpp

Index: samplecode/SampleApp.cpp
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index 1b4a55e5dd0a88d93d6fc730e9223d20e9c6528d..3d2aa7c57399cb0a570a11650d8072b067e4df6e 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -259,8 +259,12 @@ public:
 
     virtual void tearDownBackend(SampleWindow *win) {
 #if SK_SUPPORT_GPU
-        SkSafeUnref(fCurContext);
-        fCurContext = NULL;
+        if (fCurContext) {
+            // in case we have outstanding refs to this guy (lua?)
+            fCurContext->abandonContext();
+            fCurContext->unref();
+            fCurContext = NULL;
+        }
 
         SkSafeUnref(fCurIntf);
         fCurIntf = NULL;