Add ability to output ImageBaseGSUrl to render_picture and use in rebaseline server

tools/image_expectations.h

Index: tools/image_expectations.h
diff --git a/tools/image_expectations.h b/tools/image_expectations.h
index ae1df193548f90fec65f73af9e12b722539b6b64..d920ec618c9279ae9f3d7f49bcf3c570d348f9fe 100644
--- a/tools/image_expectations.h
+++ b/tools/image_expectations.h
@@ -119,6 +119,13 @@ namespace sk_tools {
         void addDescription(const char *key, const char *value);
 
         /**
+         * Adds a Google Storage Bucket to the summary of results.
+         *
+         * @param bucket the Google Storage bucket
+         */
+        void setGoogleStorageBucket(const char *bucket);
+
+        /**
          * Returns true if this test result matches its expectations.
          * If there are no expectations for this test result, this will return false.
          *
@@ -151,6 +158,7 @@ namespace sk_tools {
         Json::Value fDescriptions;
         Json::Value fExpectedJsonRoot;
         Json::Value fExpectedResults;
+        Json::Value fGoogleStorageBucket;
     };
 
 } // namespace sk_tools