Make peekPixels() usable with raster surface snapshots

include/core/SkPixmap.h

Index: include/core/SkPixmap.h
diff --git a/include/core/SkPixmap.h b/include/core/SkPixmap.h
index 05c710173593ba9ca9ec9f5705a7f077d51d5ef1..faae85e797e7f262f63a165f2fa9e690779236c2 100644
--- a/include/core/SkPixmap.h
+++ b/include/core/SkPixmap.h
@@ -18,7 +18,7 @@ struct SkMask;
  *  Pairs SkImageInfo with actual pixels and rowbytes. This class does not try to manage the
  *  lifetime of the pixel memory (nor the colortable if provided).
  */
-class SkPixmap {
+class SK_API SkPixmap {
 public:
     SkPixmap()
         : fPixels(NULL), fCTable(NULL), fRowBytes(0), fInfo(SkImageInfo::MakeUnknown(0, 0))
@@ -151,7 +151,7 @@ private:
 
 /////////////////////////////////////////////////////////////////////////////////////////////
 
-class SkAutoPixmapStorage : public SkPixmap {
+class SK_API SkAutoPixmapStorage : public SkPixmap {
 public:
     SkAutoPixmapStorage();
     ~SkAutoPixmapStorage();
@@ -206,7 +206,7 @@ private:
 
 /////////////////////////////////////////////////////////////////////////////////////////////
 
-class SkAutoPixmapUnlock : ::SkNoncopyable {
+class SK_API SkAutoPixmapUnlock : ::SkNoncopyable {
 public:
     SkAutoPixmapUnlock() : fUnlockProc(NULL), fIsLocked(false) {}
     SkAutoPixmapUnlock(const SkPixmap& pm, void (*unlock)(void*), void* ctx)