add --readJsonSummaryPath to render_pictures

tools/render_pictures_main.cpp

Index: tools/render_pictures_main.cpp
diff --git a/tools/render_pictures_main.cpp b/tools/render_pictures_main.cpp
index 1bc4d21e33098edc3cb5a0f06f9b3fdce9a99bfc..2d17c2a52631a7d9090f156d2c5ffc76ac24cf45 100644
--- a/tools/render_pictures_main.cpp
+++ b/tools/render_pictures_main.cpp
@@ -31,6 +31,7 @@ DECLARE_bool(deferImageDecoding);
 DEFINE_int32(maxComponentDiff, 256, "Maximum diff on a component, 0 - 256. Components that differ "
              "by more than this amount are considered errors, though all diffs are reported. "
              "Requires --validate.");
+DEFINE_string(readJsonSummaryPath, "", "JSON file to read image expectations from.");
 DECLARE_string(readPath);
 DEFINE_bool(writeChecksumBasedFilenames, false,
             "When writing out images, use checksum-based filenames.");
@@ -348,9 +349,10 @@ static bool render_picture(const SkString& inputPath, const SkString* outputDir,
         outputPath.append(".png");
 
         if (NULL != jsonSummaryPtr) {
+            sk_tools::ImageDigest imageDigest(*bitmap);
             SkString outputFileBasename;
             sk_tools::get_basename(&outputFileBasename, outputPath);
-            jsonSummaryPtr->add(inputFilename.c_str(), outputFileBasename.c_str(), *bitmap);
+            jsonSummaryPtr->add(inputFilename.c_str(), outputFileBasename.c_str(), imageDigest);
         }
 
         if (NULL != outputDir) {
@@ -453,6 +455,9 @@ int tool_main(int argc, char** argv) {
     sk_tools::ImageResultsSummary* jsonSummaryPtr = NULL;
     if (FLAGS_writeJsonSummaryPath.count() == 1) {
         jsonSummaryPtr = &jsonSummary;
+        if (FLAGS_readJsonSummaryPath.count() == 1) {
+            SkASSERT(jsonSummary.readExpectationsFile(FLAGS_readJsonSummaryPath[0]));
+        }
     }
 
     int failures = 0;