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

skia/ext/vector_canvas.h

Index: skia/ext/vector_canvas.h
===================================================================
--- skia/ext/vector_canvas.h	(revision 78242)
+++ skia/ext/vector_canvas.h	(working copy)
@@ -19,7 +19,7 @@
 // to work with a VectorDevice to manage platform-specific drawing. It allows
 // using both Skia operations and platform-specific operations. It *doesn't*
 // support reading back from the bitmap backstore since it is not used.
-class VectorCanvas : public PlatformCanvas {
+class SK_API VectorCanvas : public PlatformCanvas {
  public:
   VectorCanvas();
   explicit VectorCanvas(SkDeviceFactory* factory);