Address two fuzzer bugs

src/core/SkBitmap.cpp

 /*
  * Copyright 2008 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 "SkAtomics.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
@@ skipping 1127 matching lines @@
 
 bool SkBitmap::ReadRawPixels(SkReadBuffer* buffer, SkBitmap* bitmap) {
     const size_t snugRB = buffer->readUInt();
     if (0 == snugRB) {  // no pixels
         return false;
     }
 
     SkImageInfo info;
     info.unflatten(*buffer);
 
-    // If there was an error reading "info", don't use it to compute minRowBytes()
-    if (!buffer->validate(true)) {
+    // If there was an error reading "info" or if it is bogus, 
+    // don't use it to compute minRowBytes()
+    if (!buffer->validate(SkColorTypeValidateAlphaType(info.colorType(),
+                                                       info.alphaType()))) {
         return false;
     }
 
     const size_t ramRB = info.minRowBytes();
     const int height = SkMax32(info.height(), 0);
     const uint64_t snugSize = sk_64_mul(snugRB, height);
     const uint64_t ramSize = sk_64_mul(ramRB, height);
     static const uint64_t max_size_t = (size_t)(-1);
     if (!buffer->validate((snugSize <= ramSize) && (ramSize <= max_size_t))) {
         return false;
@@ skipping 187 matching lines @@
 ///////////////////////////////////////////////////////////////////////////////
 
 #ifdef SK_DEBUG
 void SkImageInfo::validate() const {
     SkASSERT(fWidth >= 0);
     SkASSERT(fHeight >= 0);
     SkASSERT(SkColorTypeIsValid(fColorType));
     SkASSERT(SkAlphaTypeIsValid(fAlphaType));
 }
 #endif