when we disable lcd for impl reasons, add kGenA8 to document the original intent

src/core/SkBitmapDevice.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkConfig8888.h"
 #include "SkDraw.h"
@@ skipping 368 matching lines @@
         // we're cool with the paint as is
         return false;
     }
 
     if (kN32_SkColorType != fBitmap.colorType() ||
         paint.getRasterizer() ||
         paint.getPathEffect() ||
         paint.isFakeBoldText() ||
         paint.getStyle() != SkPaint::kFill_Style ||
         !SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode)) {
-        // turn off lcd
+        // turn off lcd, but turn on kGenA8
         flags->fFlags = paint.getFlags() & ~SkPaint::kLCDRenderText_Flag;
-        flags->fHinting = paint.getHinting();
+        flags->fFlags |= SkPaint::kGenA8FromLCD_Flag;
         return true;
     }
     // we're cool with the paint as is
     return false;
 }