Remove user specified typeface id.

Now that there may be multiple font managers in a process the typeface
ids must be unique across all typefaces, not just unique within a font
manager. If two typefaces have the same id there will be issues in the
glyph cache. All existing font managers were already doing this by
calling SkFontCache::NewFontID, so centralize this in SkTypeface.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2147733002

Review-Url: https://codereview.chromium.org/2147733002
diff --git a/src/ports/SkFontMgr_custom.cpp b/src/ports/SkFontMgr_custom.cpp
index 0fc5180..a05cc9b 100644
--- a/src/ports/SkFontMgr_custom.cpp
+++ b/src/ports/SkFontMgr_custom.cpp
@@ -30,7 +30,7 @@
 public:
     SkTypeface_Custom(const SkFontStyle& style, bool isFixedPitch,
                       bool sysFont, const SkString familyName, int index)
-        : INHERITED(style, SkTypefaceCache::NewFontID(), isFixedPitch)
+        : INHERITED(style, isFixedPitch)
         , fIsSysFont(sysFont), fFamilyName(familyName), fIndex(index)
     { }