add SK_API to forward declare in canvas.h

include/core/SkCanvas.h

Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index 3043a3ee6264d4dae87fe40824370fd2da242965..6b2266a00e263b44f84a58c02984aef2ca753eb5 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -40,7 +40,7 @@ class GrRenderTarget;
 class SkCanvasState;
 
 namespace SkCanvasStateUtils {
-    SkCanvasState* CaptureCanvasState(SkCanvas*);// needs gettotalclip()
+    SK_API SkCanvasState* CaptureCanvasState(SkCanvas*);
 }
 
 /** \class SkCanvas
@@ -1310,7 +1310,8 @@ private:
     friend class SkDeferredDevice;  // needs getTopDevice()
     friend class SkSurface_Raster;  // needs getDevice()
     
-    friend SkCanvasState* SkCanvasStateUtils::CaptureCanvasState(SkCanvas*);// needs gettotalclip()
+    // needs gettotalclip()
+    friend SkCanvasState* SkCanvasStateUtils::CaptureCanvasState(SkCanvas*);
     
     SkBaseDevice* createLayerDevice(const SkImageInfo&);