Reland "Clean up Test's resourcePath code."

This relands commit 91359bed48bc006a4319da86eb26db3b2e6d4afb (Clean up
Test's resourcePath code."

BUG=None
TEST=make dm && out/Debug/dm
R=mtklein@google.com

Author: tfarina@chromium.org

Review URL: https://codereview.chromium.org/321723002
diff --git a/gm/factory.cpp b/gm/factory.cpp
index bd79c9d..aa643a2 100644
--- a/gm/factory.cpp
+++ b/gm/factory.cpp
@@ -28,8 +28,7 @@
 protected:
     virtual void onOnceBeforeDraw() SK_OVERRIDE {
         // Copyright-free file from http://openclipart.org/detail/29213/paper-plane-by-ddoo
-        SkString filename = SkOSPath::SkPathJoin(INHERITED::gResourcePath.c_str(),
-                                                 "plane.png");
+        SkString filename = SkOSPath::SkPathJoin(INHERITED::gResourcePath, "plane.png");
         SkAutoDataUnref data(SkData::NewFromFileName(filename.c_str()));
         if (NULL != data.get()) {
             // Create a cache which will boot the pixels out anytime the