Make SkAssertResult work with SK_WARN_UNUSED_RESULT in Release on gcc

include/core/SkTypes.h

 /*
  * 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.
  */
 
 #ifndef SkTypes_DEFINED
 #define SkTypes_DEFINED
 
@@ skipping 131 matching lines @@
     #define SkAssertResult(cond)        SkASSERT(cond)
 #else
     #define SkASSERT(cond)
     #define SkDEBUGFAIL(message)
     #define SkDEBUGCODE(code)
     #define SkDEBUGF(args)
     #define SkDECLAREPARAM(type, var)
     #define SkPARAM(var)
 
     // unlike SkASSERT, this guy executes its condition in the non-debug build.
-    // It casts to void to allow use with functions declared with SK_WARN_RESULT_UNUSED.
-    #define SkAssertResult(cond)        (void)(cond)
+    // The if is present so that this can be used with functions marked SK_WARN_UNUSED_RESULT.
+    #define SkAssertResult(cond)         if (cond) {} do {} while(false)
 #endif
 
 // Legacy macro names for SK_ABORT
 #define SkFAIL(message)                 SK_ABORT(message)
 #define sk_throw()                      SK_ABORT("sk_throw")
 
 // We want to evaluate cond only once, and inside the SkASSERT somewhere so we see its string form.
 // So we use the comma operator to make an SkDebugf that always returns false: we'll evaluate cond,
 // and if it's true the assert passes; if it's false, we'll print the message and the assert fails.
 #define SkASSERTF(cond, fmt, ...)       SkASSERT((cond) || (SkDebugf(fmt"\n", __VA_ARGS__), false))
@@ skipping 537 matching lines @@
 
     void*       fPtr;
     size_t      fSize;  // can be larger than the requested size (see kReuse)
     uint32_t    fStorage[kSize >> 2];
 };
 // Can't guard the constructor because it's a template class.
 
 #endif /* C++ */
 
 #endif