make emptypath portable; add 565 color utility

tools/sk_tool_utils.cpp

Index: tools/sk_tool_utils.cpp
diff --git a/tools/sk_tool_utils.cpp b/tools/sk_tool_utils.cpp
index 6fcd33751f3c8aa56dfe87d741c7b8265caa8f43..ec7942b165e7a77026c827320df3fc8c3ae16000 100644
--- a/tools/sk_tool_utils.cpp
+++ b/tools/sk_tool_utils.cpp
@@ -34,6 +34,12 @@ const char* colortype_name(SkColorType ct) {
     }
 }
 
+void color_to_565(SkColor* color) {
+    SkPMColor pmColor = SkPreMultiplyColor(*color);
+    U16CPU color16 = SkPixel32ToPixel16(pmColor);
+    *color = SkPixel16ToColor(color16);
+}
+
 SkTypeface* create_portable_typeface(const char* name, SkTypeface::Style style) {
     SkTypeface* face;
     if (FLAGS_portableFonts) {