Add plumbing in blink to allow overriding the default font collection.

third_party/WebKit/Source/platform/fonts/win/FontCacheSkiaWin.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Computer, Inc.
  * Copyright (c) 2006, 2007, 2008, 2009, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 79 matching lines @@
 // static
 void FontCache::setStatusFontMetrics(const wchar_t* familyName, int32_t fontHeight)
 {
     s_statusFontFamilyName = new AtomicString(familyName);
     s_statusFontHeight = ensureMinimumFontHeightIfNeeded(fontHeight);
 }
 
 FontCache::FontCache()
     : m_purgePreventCount(0)
 {
-    SkFontMgr* fontManager;
-
-    if (s_useDirectWrite) {
-        fontManager = SkFontMgr_New_DirectWrite(s_directWriteFactory);
-        s_useSubpixelPositioning = true;
+    if (s_fontManager) {
+        m_fontManager = skia::SharePtr(s_fontManager);
+    } else if (s_useDirectWrite) {
+        m_fontManager = skia::AdoptRef(SkFontMgr_New_DirectWrite(s_directWriteFactory));

[bungeman-chromium, 2016/01/21 15:48:13]

This appears to be the only place s_directWriteFactory is used. It appears that
with this code change this branch will never be taken, so s_directWriteFactory
and related should be removed.

[Ilya Kulshin, 2016/01/21 20:59:22]

s_useDirectWrite is set via setUseDirectWrite, which is still called from
https://code.google.com/p/chromium/codesearch#chromium/src/content/renderer/r...
and
https://code.google.com/p/chromium/codesearch#chromium/src/content/ppapi_plug....
setDirectWriteFactory can still be called from
https://code.google.com/p/chromium/codesearch#chromium/src/content/common/fon...,
which is called if ShouldUseDirectWriteFontProxyFieldTrial returns false. For
now, it is still needed, but I will make a note to remove it when deleting the
old chrome font cache codepath.

[bungeman-skia, 2016/01/21 21:11:40]

Sure, s_useDirectWrite is still called (and should also be removed) but you'll
still never get here, because every path which will set it to true will also
already have set the s_fontManager (and if it doesn't, it should be).

In other words, this CL is adding code to support s_directWriteFactory and
s_useDirectWrite, but it doesn't seem that this is necessary (or wanted).

     } else {
-        fontManager = SkFontMgr_New_GDI();
-        // Subpixel text positioning is not supported by the GDI backend.
-        s_useSubpixelPositioning = false;
+        m_fontManager = skia::AdoptRef(SkFontMgr_New_GDI());
     }
 
-    ASSERT(fontManager);
-    m_fontManager = adoptPtr(fontManager);
+    // Subpixel text positioning is only supported by the DirectWrite backend (not GDI).
+    s_useSubpixelPositioning = s_useDirectWrite;
+
+    ASSERT(m_fontManager.get());
 }
 
 
 // Given the desired base font, this will create a SimpleFontData for a specific
 // font that can be used to render the given range of characters.
 PassRefPtr<SimpleFontData> FontCache::fallbackFontForCharacter(
     const FontDescription& fontDescription, UChar32 character,
     const SimpleFontData* originalFontData)
 {
     // First try the specified font with standard style & weight.
@@ skipping 297 matching lines @@
         if (typefacesMatchesFamily(tf.get(), family)) {
             result->setMinSizeForSubpixel(minSizeForSubpixelForFont);
             break;
         }
     }
 
     return result.release();
 }
 
 } // namespace blink