Prevent malformed ICO files from recursively decoding

R=reed@google.com, scroggo@google.com

Author: djsollen@google.com

Review URL: https://codereview.chromium.org/511453002

bug:17265466,17262540
Change-Id: I128b54c74d75b7afca20e47e6650c500278c5adc

Author: drWulf

src/images/SkImageDecoder_libico.cpp

@@ -160,6 +160,10 @@ bool SkICOImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode)
         SkMemoryStream subStream(buf + offset, size, false);
         SkAutoTDelete<SkImageDecoder> otherDecoder(SkImageDecoder::Factory(&subStream));
         if (otherDecoder.get() != NULL) {
+            // Disallow nesting ICO files within one another
+            if (otherDecoder->getFormat() == SkImageDecoder::kICO_Format) {
+                return false;
+            }
             // Set fields on the other decoder to be the same as this one.
             this->copyFieldsToOther(otherDecoder.get());
             if(otherDecoder->decode(&subStream, bm, this->getDefaultPref(), mode)) {