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

skia/ext/platform_canvas.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SKIA_EXT_PLATFORM_CANVAS_H_
 #define SKIA_EXT_PLATFORM_CANVAS_H_
 #pragma once
 
 // The platform-specific device will include the necessary platform headers
 // to get the surface type.
 #include "skia/ext/platform_device.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace skia {
 
 // This class is a specialization of the regular SkCanvas that is designed to
 // work with a PlatformDevice to manage platform-specific drawing. It allows
 // using both Skia operations and platform-specific operations.
-class PlatformCanvas : public SkCanvas {
+class SK_API PlatformCanvas : public SkCanvas {
  public:
   // If you use the version with no arguments, you MUST call initialize()
   PlatformCanvas();
   explicit PlatformCanvas(SkDeviceFactory* factory);
   // Set is_opaque if you are going to erase the bitmap and not use
   // transparency: this will enable some optimizations.
   PlatformCanvas(int width, int height, bool is_opaque);
 
 #if defined(WIN32)
   // The shared_section parameter is passed to gfx::PlatformDevice::create.
@@ skipping 80 matching lines @@
   virtual SkDevice* setBitmapDevice(const SkBitmap& bitmap);
 
   // Disallow copy and assign.
   PlatformCanvas(const PlatformCanvas&);
   PlatformCanvas& operator=(const PlatformCanvas&);
 };
 
 }  // namespace skia
 
 #endif  // SKIA_EXT_PLATFORM_CANVAS_H_