Build skia as a dll in windows multi-dll build.

skia/config/SkUserConfig.h

 /*
  * Copyright (C) 2006 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
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  */
 #define SK_DISABLE_DITHER_32BIT_GRADIENT
 
 // ===== Begin Chrome-specific definitions =====
 
 #define SK_SCALAR_IS_FLOAT
 #undef SK_SCALAR_IS_FIXED
 
 // Log the file and line number for assertions.
 #define SkDebugf(...) SkDebugf_FileLine(__FILE__, __LINE__, false, __VA_ARGS__)
-void SkDebugf_FileLine(const char* file, int line, bool fatal,
-                       const char* format, ...);
+SK_API void SkDebugf_FileLine(const char* file, int line, bool fatal,
+                              const char* format, ...);
 
 // Marking the debug print as "fatal" will cause a debug break, so we don't need
 // a separate crash call here.
 #define SK_DEBUGBREAK(cond) do { if (!(cond)) { \
     SkDebugf_FileLine(__FILE__, __LINE__, true, \
     "%s:%d: failed assertion \"%s\"\n", \
     __FILE__, __LINE__, #cond); } } while (false)
 
 // All little-endian Chrome platforms agree:  BGRA is the optimal pixel layout.
 #define SK_A32_SHIFT    24
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 #endif
 
 // The default crash macro writes to badbeef which can cause some strange
 // problems. Instead, pipe this through to the logging function as a fatal
 // assertion.
 #define SK_CRASH() SkDebugf_FileLine(__FILE__, __LINE__, true, "SK_CRASH")
 
 // ===== End Chrome-specific definitions =====
 
 #endif