Implement support for rendering color emoji on Windows

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 7343ce4744e661bd5a08600fb58df0d202c6d253..2317573e09123eef79bd2d281d3aa862e3a7174c 100644
--- a/tools/sk_tool_utils.cpp
+++ b/tools/sk_tool_utils.cpp
@@ -72,6 +72,9 @@ const char* platform_os_emoji() {
     if (!strncmp(osName, "Mac", 3)) {
         return "SBIX";
     }
+    if (!strncmp(osName, "Win", 3)) {
+        return "COLR";
+    }
     return "";
 }
 
@@ -82,6 +85,9 @@ sk_sp<SkTypeface> emoji_typeface() {
     if (!strcmp(sk_tool_utils::platform_os_emoji(), "SBIX")) {
         return SkTypeface::MakeFromName("Apple Color Emoji", SkTypeface::kNormal);
     }
+    if (!strcmp(sk_tool_utils::platform_os_emoji(), "COLR")) {
+        return SkTypeface::MakeFromName("Segoe UI Emoji", SkTypeface::kNormal);

[bungeman-skia, 2016/05/26 19:49:35]

After running the trybots on this and taking a look at the output, it's rather
unfortunate what is happening on win7 for these tests. Since they don't have
Segoe UI Emoji this comes back with the default font instead of nullptr, which
means that several of the tests draw empty squares on win7, since that font
doesn't have these glyphs. Instead, if we make the body of this block more like

        sk_sp<SkFontMgr> fm(SkFontMgr::RefDefault());
        sk_sp<SkTypeface> typeface(fm->matchFamilyStyle("Segoe UI Emoji",
SkFontStyle()));
        if (typeface) {
            return typeface;
        }
        // Windows 7 does not have Segoe UI Emoji; Segoe UI Symbol has the
(non-color) emoji.
        return SkTypeface::MakeFromName("Segoe UI Symbol", SkTypeface::kNormal);

then the output on win7 doesn't look quite so confusingly bad. Basically this
just says to get Segoe UI Emoji if it exists, if it doesn't exist try to get
Segoe UI Symbol, otherwise get the default system font which will draw bad so we
can see that we did something bad. On the other hand, I can just make this
change after this lands.

[Ilya Kulshin, 2016/05/27 04:59:17]

Done, although since this was creating the font manager anyway, I added code to
use the font fallback API to possibly pick a font if Segoe UI Emoji is not
available. I think with the fallback it doesn't even need to try to fallback on
Segoe UI Symbol, but I'm having some trouble building Skia on my Win7 machine so
I haven't tried it out yet. Hopefully I'll be able to try it out tomorrow - if
it can figure out the fallback on Win7 then it won't need the explicit fallback
on Segoe UI Symbol and I'll remove it.

+    }
     return nullptr;
 }
 
@@ -89,7 +95,9 @@ const char* emoji_sample_text() {
     if (!strcmp(sk_tool_utils::platform_os_emoji(), "CBDT")) {
         return "Hamburgefons";
     }
-    if (!strcmp(sk_tool_utils::platform_os_emoji(), "SBIX")) {
+    if (!strcmp(sk_tool_utils::platform_os_emoji(), "SBIX") ||
+        !strcmp(sk_tool_utils::platform_os_emoji(), "COLR"))
+    {
         return "\xF0\x9F\x92\xB0" "\xF0\x9F\x8F\xA1" "\xF0\x9F\x8E\x85"  // 💰🏡🎅
                "\xF0\x9F\x8D\xAA" "\xF0\x9F\x8D\x95" "\xF0\x9F\x9A\x80"  // 🍪🍕🚀
                "\xF0\x9F\x9A\xBB" "\xF0\x9F\x92\xA9" "\xF0\x9F\x93\xB7" // 🚻💩📷