GM: make behavior of make_filename() more late-binding

gm/gmmain.cpp

Index: gm/gmmain.cpp
===================================================================
--- gm/gmmain.cpp	(revision 9186)
+++ gm/gmmain.cpp	(working copy)
@@ -192,6 +192,17 @@
     GMMain() : fUseFileHierarchy(false), fIgnorableErrorTypes(kDefaultIgnorableErrorTypes),
                fMismatchPath(NULL), fTestsRun(0), fRenderModesEncountered(1) {}
 
+    SkString make_filename(const char path[],
+                           const char renderModeDescriptor[],
+                           const char *name,
+                           const char suffix[]) {
+        SkString filename(name);
+        filename.append(renderModeDescriptor);
+        filename.appendUnichar('.');
+        filename.append(suffix);
+        return SkPathJoin(path, filename.c_str());
+    }
+
     SkString make_name(const char shortName[], const char configName[]) {
         SkString name;
         if (0 == strlen(configName)) {
@@ -1570,8 +1581,8 @@
     if ((1 == FLAGS_writePicturePath.count()) &&
         !(gmFlags & GM::kSkipPicture_Flag)) {
         const char* pictureSuffix = "skp";
-        SkString path = make_filename(FLAGS_writePicturePath[0], "",
-                                      gm->shortName(), pictureSuffix);
+        SkString path = gmmain.make_filename(FLAGS_writePicturePath[0], "",
+                                             gm->shortName(), pictureSuffix);
         SkFILEWStream stream(path.c_str());
         pict->serialize(&stream);
     }