make tests portable by using 565 compatible colors

TBR=reed@google.com

Review URL: https://codereview.chromium.org/1262703002
diff --git a/gm/matriximagefilter.cpp b/gm/matriximagefilter.cpp
index 419c419..b4242a7 100644
--- a/gm/matriximagefilter.cpp
+++ b/gm/matriximagefilter.cpp
@@ -41,9 +41,9 @@
         bitmap->allocN32Pixels(64, 64);
         SkCanvas canvas(*bitmap);
         SkPaint darkPaint;
-        darkPaint.setColor(0xFF404040);
+        darkPaint.setColor(sk_tool_utils::color_to_565(0xFF404040));
         SkPaint lightPaint;
-        lightPaint.setColor(0xFFA0A0A0);
+        lightPaint.setColor(sk_tool_utils::color_to_565(0xFFA0A0A0));
         for (int y = 0; y < 64; y += 32) {
             for (int x = 0; x < 64; x += 32) {
                 canvas.save();