Begin atlasing

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 850053cfc6f9b258469ac8ab3077f81cd378b2f8..da2a744c40438b071124ba0dcdcdaf12d68e6a63 100644
--- a/tools/render_pictures_main.cpp
+++ b/tools/render_pictures_main.cpp
@@ -212,6 +212,12 @@ static bool render_picture_internal(const SkString& inputPath, const SkString* w
         SkDebugf("Failed to render %s\n", inputFilename.c_str());
     }
 
+    if (FLAGS_preprocess) {
+        if (NULL != renderer.getCanvas()) {
+            renderer.getCanvas()->EXPERIMENTAL_purge(renderer.getPicture());
+        }
+    }
+
     renderer.end();
 
     SkDELETE(picture);