Refactor how we handle resources path in Tests.

This idea emerged while doing https://codereview.chromium.org/321723002/
(commit 880914c35c8f7fc2e9c57134134c883baf66e538).

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

Author: tfarina@chromium.org

Review URL: https://codereview.chromium.org/346453002
diff --git a/bench/ETCBitmapBench.cpp b/bench/ETCBitmapBench.cpp
index e9aee76..d5f32db 100644
--- a/bench/ETCBitmapBench.cpp
+++ b/bench/ETCBitmapBench.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include "Resources.h"
 #include "SkBenchmark.h"
 #include "SkCanvas.h"
 #include "SkData.h"