Fixes for SkPictureShader.

tests/PictureShaderTest.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPicture.h"
+#include "SkPictureRecorder.h"
+#include "SkShader.h"
+#include "Test.h"
+
+// Test that attempting to create a picture shader with a NULL picture or
+// empty picture returns NULL.
+DEF_TEST(PictureShader_empty, reporter) {
+    SkShader* shader = SkShader::CreatePictureShader(NULL,
+            SkShader::kClamp_TileMode, SkShader::kClamp_TileMode);
+    REPORTER_ASSERT(reporter, NULL == shader);
+
+    SkPictureRecorder factory;
+    factory.beginRecording(0, 0, NULL, 0);
+    SkAutoTUnref<SkPicture> picture(factory.endRecording());
+    shader = SkShader::CreatePictureShader(picture.get(),
+            SkShader::kClamp_TileMode, SkShader::kClamp_TileMode);
+    REPORTER_ASSERT(reporter, NULL == shader);
+}