guard against self-assignment

src/core/SkPaint.cpp

 
 /*
  * Copyright 2006 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 "SkPaint.h"
 #include "SkAnnotation.h"
@@ skipping 135 matching lines @@
     SkSafeUnref(fXfermode);
     SkSafeUnref(fMaskFilter);
     SkSafeUnref(fColorFilter);
     SkSafeUnref(fRasterizer);
     SkSafeUnref(fLooper);
     SkSafeUnref(fImageFilter);
     SkSafeUnref(fAnnotation);
 }
 
 SkPaint& SkPaint::operator=(const SkPaint& src) {
+    if (this == &src) {
+        return *this;
+    }
+
 #define COPY(field) field = src.field
 #define REF_COPY(field) SkSafeUnref(field); field = SkSafeRef(src.field)
 
     SkASSERT(&src);
 
     REF_COPY(fTypeface);
     REF_COPY(fPathEffect);
     REF_COPY(fShader);
     REF_COPY(fXfermode);
     REF_COPY(fMaskFilter);
@@ skipping 2561 matching lines @@
     }
 #ifdef SK_BUILD_FOR_ANDROID
     if (dirty & kPaintOptionsAndroid_DirtyBit) {
         SkPaintOptionsAndroid options;
         options.unflatten(buffer);
         paint->setPaintOptionsAndroid(options);
     }
 #endif
     SkASSERT(dirty == paint->fDirtyBits);
 }