make tests portable by using 565 compatible colors

TBR=reed@google.com

Review URL: https://codereview.chromium.org/1262703002
diff --git a/gm/lighting.cpp b/gm/lighting.cpp
index 6df5851..b721fef 100644
--- a/gm/lighting.cpp
+++ b/gm/lighting.cpp
@@ -58,9 +58,9 @@
             make_bitmap();
             fInitialized = true;
         }
-        canvas->clear(0xFF101010);
+        canvas->clear(sk_tool_utils::color_to_565(0xFF101010));
         SkPaint checkPaint;
-        checkPaint.setColor(0xFF202020);
+        checkPaint.setColor(sk_tool_utils::color_to_565(0xFF202020));
         for (int y = 0; y < HEIGHT; y += 16) {
           for (int x = 0; x < WIDTH; x += 16) {
             canvas->save();