Ensure that we create a NULL codec for images with zero dimensions

src/codec/SkCodec_libbmp.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodec_libbmp.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
@@ skipping 301 matching lines @@
     RowOrder rowOrder = kBottomUp_RowOrder;
     if (height < 0) {
         height = -height;
         rowOrder = kTopDown_RowOrder;
     }
     // The height field for bmp in ico is double the actual height because they
     // contain an XOR mask followed by an AND mask
     if (isIco) {
         height /= 2;
     }
-    static const int kBmpMaxDim = 1 << 16;
-    if (width < 0 || width >= kBmpMaxDim || height >= kBmpMaxDim) {
-        // TODO: Decide if we want to support really large bmps.
+    if (width <= 0 || height <= 0) {
+        // TODO: Decide if we want to disable really large bmps as well.
+        // https://code.google.com/p/skia/issues/detail?id=3617
         SkCodecPrintf("Error: invalid bitmap dimensions.\n");
         return false;
     }
 
     // Create mask struct
     SkMasks::InputMasks inputMasks;
     memset(&inputMasks, 0, sizeof(SkMasks::InputMasks));
 
     // Determine the input compression format and set bit masks if necessary
     uint32_t maskBytes = 0;
@@ skipping 894 matching lines @@
                 uint32_t alphaBit =
                         (srcBuffer.get()[quotient] >> shift) & 0x1;
                 dstRow[x] &= alphaBit - 1;
             }
         }
     }
 
     // Finished decoding the entire image
     return kSuccess;
 }