Initial error handling code

src/effects/SkMergeImageFilter.cpp

Index: src/effects/SkMergeImageFilter.cpp
diff --git a/src/effects/SkMergeImageFilter.cpp b/src/effects/SkMergeImageFilter.cpp
index 0c47c91aff21d73e4da6738682da3d2f7d044657..a3a9f0909746280dbc5c0e596412d2d2c058b33d 100755
--- a/src/effects/SkMergeImageFilter.cpp
+++ b/src/effects/SkMergeImageFilter.cpp
@@ -9,6 +9,7 @@
 #include "SkCanvas.h"
 #include "SkDevice.h"
 #include "SkFlattenableBuffers.h"
+#include "SkValidation.h"
 
 ///////////////////////////////////////////////////////////////////////////////
 
@@ -157,8 +158,12 @@ SkMergeImageFilter::SkMergeImageFilter(SkFlattenableReadBuffer& buffer) : INHERI
     bool hasModes = buffer.readBool();
     if (hasModes) {
         this->initAllocModes();
-        SkASSERT(buffer.getArrayCount() == countInputs() * sizeof(fModes[0]));
+        int nbInputs = countInputs();
+        SkASSERT(buffer.getArrayCount() == nbInputs * sizeof(fModes[0]));
         buffer.readByteArray(fModes);
+        for (int i = 0; i < nbInputs; ++i) {
+            buffer.validateData(IsValidMode((SkXfermode::Mode)fModes[i]));
+        }
     } else {
         fModes = 0;
     }