Add scaled emoji GM.

Draws string at four scales to test each method of emoji rendering.

Bug: skia:7562
Change-Id: Id28fea702aef36e3d2d5a9ca24c1685517979b3c
Reviewed-on: https://skia-review.googlesource.com/107020
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

gm/scaledemoji.cpp

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+#include "sk_tool_utils.h"
+
+#include "Resources.h"
+#include "SkCanvas.h"
+#include "SkStream.h"
+#include "SkTypeface.h"
+
+namespace skiagm {
+
+class ScaledEmojiGM : public GM {
+public:
+    ScaledEmojiGM() { }
+
+protected:
+    struct EmojiFont {
+        sk_sp<SkTypeface> fTypeface;
+        const char* fText;
+    } fEmojiFont;
+
+    void onOnceBeforeDraw() override {
+        fEmojiFont.fTypeface = sk_tool_utils::emoji_typeface();
+        fEmojiFont.fText = sk_tool_utils::emoji_sample_text();
+    }
+
+    SkString onShortName() override {
+        SkString name("scaledemoji");
+        name.append(sk_tool_utils::platform_font_manager());
+        return name;
+    }
+
+    SkISize onISize() override { return SkISize::Make(1200, 1200); }
+
+    void onDraw(SkCanvas* canvas) override {
+
+        canvas->drawColor(sk_tool_utils::color_to_565(SK_ColorGRAY));
+
+        SkPaint paint;
+        paint.setTypeface(fEmojiFont.fTypeface);
+        const char* text = fEmojiFont.fText;
+
+        // draw text at different point sizes
+        // Testing GPU bitmap path, SDF path with no scaling,
+        // SDF path with scaling, path rendering with scaling
+        SkPaint::FontMetrics metrics;
+        SkScalar y = 0;
+        for (SkScalar textSize : { 70, 180, 270, 340 }) {
+            paint.setTextSize(textSize);
+            paint.getFontMetrics(&metrics);
+            y += -metrics.fAscent;
+            canvas->drawString(text, 10, y, paint);
+            y += metrics.fDescent + metrics.fLeading;
+        }
+
+    }
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM(return new ScaledEmojiGM;)
+
+}

gn/gm.gni

@@ -262,6 +262,7 @@ gm_sources = [
   "$_gm/samplerstress.cpp",
   "$_gm/savelayer.cpp",
   "$_gm/scaledstrokes.cpp",
+  "$_gm/scaledemoji.cpp",
   "$_gm/shadermaskfilter.cpp",
   "$_gm/shadertext.cpp",
   "$_gm/shadertext2.cpp",