setDrawFilter needs to trigger any deferred saves

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/1077353002
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 7949cb3..68ced60 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -589,6 +589,7 @@
 }
 
 SkDrawFilter* SkCanvas::setDrawFilter(SkDrawFilter* filter) {
+    this->checkForDeferredSave();
     SkRefCnt_SafeAssign(fMCRec->fFilter, filter);
     return filter;
 }