Allow the resource cache to (indirectly) flush the InOrderDrawBuffer

R=bsalomon@google.com

Author: robertphillips@google.com

Review URL: https://chromiumcodereview.appspot.com/18466005

git-svn-id: http://skia.googlecode.com/svn/trunk@9949 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 9f3c9f6..09be365 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -929,6 +929,12 @@
                                            bool swapRAndB,
                                            const SkMatrix& matrix);
 
+    /**
+     *  This callback allows the resource cache to callback into the GrContext
+     *  when the cache is still overbudget after a purge.
+     */
+    static bool OverbudgetCB(void* data);
+
     typedef GrRefCnt INHERITED;
 };