setDrawFilter needs to trigger any deferred saves

tests/DrawFilterTest.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCanvas.h"
+#include "SkDrawFilter.h"
+#include "SkSurface.h"
+#include "Test.h"
+
+class TestFilter : public SkDrawFilter {
+public:
+    bool filter(SkPaint* p, Type) override {
+        return true;
+    }
+};
+
+/**
+ *  canvas.setDrawFilter is defined to be local to the save/restore block, such that if you
+ *  do the following: save / modify-drawfilter / restore, the current drawfilter should be what
+ *  it was before the save.
+ */
+static void test_saverestore(skiatest::Reporter* reporter) {
+    SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterN32Premul(10, 10));
+    SkCanvas* canvas = surface->getCanvas();
+
+
+    SkAutoTUnref<TestFilter> df(SkNEW(TestFilter));
+
+    REPORTER_ASSERT(reporter, NULL == canvas->getDrawFilter());
+
+    canvas->save();
+    canvas->setDrawFilter(df);
+    REPORTER_ASSERT(reporter, NULL != canvas->getDrawFilter());
+    canvas->restore();
+
+    REPORTER_ASSERT(reporter, NULL == canvas->getDrawFilter());
+}
+
+DEF_TEST(DrawFilter, reporter) {
+    test_saverestore(reporter);
+}