Test abandoning GL context in dm/nanobench.

include/gpu/GrContextFactory.h

Index: include/gpu/GrContextFactory.h
diff --git a/include/gpu/GrContextFactory.h b/include/gpu/GrContextFactory.h
index 1f1f89df14d1995f5751f15b13c4508ce968539f..01e0239b1a16d966587994263c1f4290bf246e94 100644
--- a/include/gpu/GrContextFactory.h
+++ b/include/gpu/GrContextFactory.h
@@ -94,13 +94,24 @@ public:
 
     void destroyContexts() {
         for (int i = 0; i < fContexts.count(); ++i) {
-            fContexts[i].fGLContext->makeCurrent();
+            if (NULL != fContexts[i].fGLContext) {  //  could be abandoned.
+                fContexts[i].fGLContext->makeCurrent();
+            }
             fContexts[i].fGrContext->unref();
-            fContexts[i].fGLContext->unref();
+            if (NULL != fContexts[i].fGLContext) {
+                fContexts[i].fGLContext->unref();
+            }
         }
         fContexts.reset();
     }
 
+    void abandonContexts() {
+        for (int i = 0; i < fContexts.count(); ++i) {
+            SkSafeSetNull(fContexts[i].fGLContext);
+            fContexts[i].fGrContext->abandonContext();
+        }
+    }
+
     /**
      * Get a GrContext initialized with a type of GL context. It also makes the GL context current.
      */