add --descriptions flag to render_pictures tool

tools/image_expectations.h

 /*
  * 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
 
@@ skipping 93 matching lines @@
          *
          * @param sourceName name of the source file that generated this result
          * @param fileName relative path to the image output file on local disk
          * @param digest description of the image's contents
          * @param tileNumber if not NULL, pointer to tile number
          */
         void add(const char *sourceName, const char *fileName, const ImageDigest &digest,
                  const int *tileNumber=NULL);
 
         /**
+         * Adds a key/value pair to the descriptions dict within the summary of results.
+         *
+         * @param key key within the descriptions dict
+         * @param value value to associate with that key
+         */
+        void addDescription(const char *key, const char *value);
+
+        /**
          * Returns true if this test result matches its expectations.
          * If there are no expectations for this test result, this will return false.
          *
          * @param sourceName name of the source file that generated this result
          * @param digest description of the image's contents
          * @param tileNumber if not NULL, pointer to tile number
          */
         bool matchesExpectation(const char *sourceName, const ImageDigest &digest,
                                 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) const;
 
     private:
 
         /**
          * Read the file contents from filePtr and parse them into jsonRoot.
          *
          * It is up to the caller to close filePtr after this is done.
          *
          * Returns true if successful.
          */
         static bool Parse(SkFILE* filePtr, Json::Value *jsonRoot);
 
         Json::Value fActualResults;
+        Json::Value fDescriptions;
         Json::Value fExpectedJsonRoot;
         Json::Value fExpectedResults;
     };
 
 } // namespace sk_tools
 
 #endif  // image_expectations_DEFINED