SkPDF: SkBitSet gets reset() to make drop() better.

src/utils/SkBitSet.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBitSet_DEFINED
 #define SkBitSet_DEFINED
 
 #include "SkTDArray.h"
 #include "SkTemplates.h"
 
 class SkBitSet {
 public:
     explicit SkBitSet(int numberOfBits) {
-        SkASSERT(numberOfBits > 0);
+        SkASSERT(numberOfBits >= 0);
         fDwordCount = (numberOfBits + 31) / 32;  // Round up size to 32-bit boundary.
-        fBitData.reset((uint32_t*)sk_calloc_throw(fDwordCount * sizeof(uint32_t)));
+        if (fDwordCount > 0) {
+            fBitData.reset((uint32_t*)sk_calloc_throw(fDwordCount * sizeof(uint32_t)));
+        }
     }
 
     SkBitSet(const SkBitSet&) = delete;
     SkBitSet& operator=(const SkBitSet&) = delete;
 
     /** Set the value of the index-th bit to true.  */
     void set(int index) {
         uint32_t mask = 1 << (index & 31);
         uint32_t* chunk = this->internalGet(index);
         SkASSERT(chunk);
@@ skipping 41 matching lines @@
         size_t internalIndex = index / 32;
         if (internalIndex >= fDwordCount) {
             return nullptr;
         }
         return fBitData.get() + internalIndex;
     }
 };
 
 
 #endif