Ammend font table data experiment on Mac.

src/ports/SkFontHost_mac.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTypes.h"  // Keep this before any #ifdef ...
 
@@ skipping 895 matching lines @@
     // However, in 10.10.2 color glyphs no longer rotate based on the font transform.
     // So always make the font transform identity and place the transform on the context.
     point = CGPointApplyAffineTransform(point, context.fInvTransform);
 
     // Attempt to keep on the stack a hard reference to the font tables.
     // This is an experiment to see if this affects crbug.com/413332 .
     // When 10.6 headers are no longer supported, 'sbix' can be replaced with kCTFontTableSbix.
     AutoCFRelease<CFDataRef> sbix;
     if (static_cast<SkTypeface_Mac*>(context.getTypeface())->fHasColorGlyphs) {
         sbix.reset(CGFontCopyTableForTag(context.fCGFont, 'sbix'));
+        // Attempt to read from the sbix table data to determine if the returned data is valid.
+        const UInt8* sbixData = CFDataGetBytePtr(sbix);
+        CFIndex sbixLength = CFDataGetLength(sbix);
+        if (sbixLength > 0 && *sbixData > 0x80) {
+            // We need to actually do something to avoid this being optimized away.
+            CFRetain(sbix);
+            CFRelease(sbix);
+        }
     }
     ctFontDrawGlyphs(context.fCTUnrotatedFont, &glyphID, &point, 1, fCG);
 
     SkASSERT(rowBytesPtr);
     *rowBytesPtr = rowBytes;
     return image;
 }
 
 void SkScalerContext_Mac::getVerticalOffset(CGGlyph glyphID, SkPoint* offset) const {
     // Snow Leopard returns cgVertOffset in completely un-transformed FUnits (em space, y up).
@@ skipping 1367 matching lines @@
         }
         return face;
     }
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkFontMgr* SkFontMgr::Factory() {
     return SkNEW(SkFontMgr_Mac);
 }