Add a SymbolsIterator to aid with Symbols Segmentation

third_party/WebKit/Source/platform/fonts/FontFallbackPriority.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "platform/fonts/FontFallbackPriority.h"
+
+namespace blink {
+
+bool isNonTextFallbackPriority(FontFallbackPriority fallbackPriority)
+{
+    return fallbackPriority == FontFallbackPriority::Symbols

[wkorman, 2016/01/22 00:50:45]

Why not return fallbackPriority != FontFallbackPriority::Text?

[drott, 2016/01/22 14:28:21]

I chose to enumerate them because I would like the next person that adds a value
to the enumeration to explicitly decide whether it's a non-text value that
requires special handling in FontFallbackIterator and FontCache (the changes to
those classes will follow in subsequent CLs).

+        || fallbackPriority == FontFallbackPriority::Math
+        || fallbackPriority == FontFallbackPriority::EmojiText
+        || fallbackPriority == FontFallbackPriority::EmojiEmoji;
+};
+
+}