Fix self assigment in GrResourceKey

include/gpu/GrResourceKey.h

 
 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrResourceKey_DEFINED
 #define GrResourceKey_DEFINED
@@ skipping 31 matching lines @@
         fKey.reset(kMetaDataCnt);
         fKey[kHash_MetaDataIdx] = 0;
         fKey[kDomainAndSize_MetaDataIdx] = kInvalidDomain;
     }
 
     bool operator==(const GrResourceKey& that) const {
         return 0 == memcmp(fKey.get(), that.fKey.get(), this->size());
     }
 
     GrResourceKey& operator=(const GrResourceKey& that) {
-        size_t bytes = that.size();
-        SkASSERT(SkIsAlign4(bytes));
-        fKey.reset(SkToInt(bytes / sizeof(uint32_t)));
-        memcpy(fKey.get(), that.fKey.get(), bytes);
+        if (this != &that) {
+            size_t bytes = that.size();
+            SkASSERT(SkIsAlign4(bytes));
+            fKey.reset(SkToInt(bytes / sizeof(uint32_t)));
+            memcpy(fKey.get(), that.fKey.get(), bytes);
+        }
         return *this;
     }
 
     bool isValid() const { return kInvalidDomain != this->domain(); }
 
     uint32_t domain() const { return fKey[kDomainAndSize_MetaDataIdx] & 0xffff; }
 
     /** Used to initialize a key. */
     class Builder {
     public:
@@ skipping 148 matching lines @@
             int innerKeyCnt = SkToInt(innerKey.size()) >> 2;
             // add the inner key to the end of the key so that op[] can be indexed normally.
             for (int i = 0; i < innerKeyCnt; ++i) {
                 this->operator[](extraData32Cnt + i) = innerKey.data()[i];
             }
         }
     };
 };
 
 #endif