extract some common code from PictureRenderer

tools/image_expectations.h

Index: tools/image_expectations.h
diff --git a/tools/image_expectations.h b/tools/image_expectations.h
new file mode 100644
index 0000000000000000000000000000000000000000..432cf6d3a80bd3f4cbe2e563c2c0d4116a47d7a5
--- /dev/null
+++ b/tools/image_expectations.h
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+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef image_expectations_DEFINED
+#define image_expectations_DEFINED
+
+#include "SkBitmap.h"
+#include "SkJSONCPP.h"
+
+namespace sk_tools {
+
+    /**
+     * Class for collecting image results (checksums) as we go.
+     */
+    class ImageResultsSummary {
+    public:
+        /**
+         * Adds this image to the summary of results.
+         *
+         * @param sourceName name of the source file that generated this result
+         * @param fileName relative path to the image output file on local disk
+         * @param hash hash to store
+         * @param tileNumber if not NULL, ptr to tile number
+         */
+        void add(const char *sourceName, const char *fileName, uint64_t hash,
+                 const int *tileNumber=NULL);
+
+        /**
+         * Adds this image to the summary of results.
+         *
+         * @param sourceName name of the source file that generated this result
+         * @param fileName relative path to the image output file on local disk
+         * @param bitmap bitmap to store the hash of
+         * @param tileNumber if not NULL, ptr to tile number
+         */
+        void add(const char *sourceName, const char *fileName, const SkBitmap& bitmap,
+                 const int *tileNumber=NULL);
+
+        /**
+         * Writes the summary (as constructed so far) to a file.
+         *
+         * @param filename path to write the summary to
+         */
+        void writeToFile(const char *filename);
+
+    private:
+        Json::Value fActualResults;
+    };
+
+} // namespace sk_tools
+
+#endif  // image_expectations_DEFINED