make tests portable by using 565 compatible colors

gm/discard.cpp

Index: gm/discard.cpp
diff --git a/gm/discard.cpp b/gm/discard.cpp
index 106a6becc06e6fbf36f40bfe45e2783dfd122957..d30e15c316000a93981b926f0071f134ecdaef96 100644
--- a/gm/discard.cpp
+++ b/gm/discard.cpp
@@ -58,7 +58,7 @@ protected:
             for (int y = 0; y < 10; ++y) {
               surface->getCanvas()->discard();
               // Make something that isn't too close to the background color, black.
-              SkColor color = rand.nextU() | 0xFF404040;
+              SkColor color = sk_tool_utils::color_to_565(rand.nextU() | 0xFF404040);
               switch (rand.nextULessThan(3)) {
                   case 0:
                       surface->getCanvas()->drawColor(color);