[TextBlob] Recompute blob bounds when empty.

Source/platform/fonts/Font.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (c) 2007, 2008, 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 238 matching lines @@
     if (cacheEntry && (!fallbackFonts || fallbackFonts->isEmpty())) {
         cacheEntry->glyphBounds = glyphBounds;
         cacheEntry->width = result;
     }
 
     if (glyphOverflow)
         updateGlyphOverflowFromBounds(glyphBounds, fontMetrics(), glyphOverflow);
     return result;
 }
 
-static bool requiresRecomputingBounds(const Font& font)
+static bool requiresRecomputingBounds(const Font& font, const FloatRect& bounds)
 {
+    // Blobs should never have empty bounds, but see http://crbug.com/445527
+    if (bounds.isEmpty())
+        return true;
+
     const FontDescription& fontDescription = font.fontDescription();
     return fontDescription.letterSpacing() < 0 || fontDescription.wordSpacing() < 0;
 }
 
 PassTextBlobPtr Font::buildTextBlob(const GlyphBuffer& glyphBuffer, const FloatRect& bounds,
     bool couldUseLCD) const
 {
     ASSERT(RuntimeEnabledFeatures::textBlobEnabled());
 
     SkTextBlobBuilder builder;
     SkRect skBounds = bounds;
     // FIXME: Identify these cases earlier on and avoid using bounds that are
     // not visually correct in other places.
-    const SkRect* skBoundsPtr = requiresRecomputingBounds(*this) ? nullptr : &skBounds;
+    const SkRect* skBoundsPtr = requiresRecomputingBounds(*this, bounds) ? nullptr : &skBounds;
     bool hasVerticalOffsets = glyphBuffer.hasVerticalOffsets();
 
     unsigned i = 0;
     while (i < glyphBuffer.size()) {
         const SimpleFontData* fontData = glyphBuffer.fontDataAt(i);
 
         // FIXME: Handle vertical text.
         if (fontData->platformData().orientation() == Vertical)
             return nullptr;
 
@@ skipping 675 matching lines @@
                 if (delta <= 0)
                     break;
             }
         }
     }
 
     return offset;
 }
 
 } // namespace blink