mark all SkImage methods const, so we can make it thread-safe

src/image/SkImage_Gpu.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkImagePriv.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "GrContext.h"
 #include "GrTexture.h"
 #include "SkGrPixelRef.h"
 
 class SkImage_Gpu : public SkImage_Base {
 public:
     SK_DECLARE_INST_COUNT(SkImage_Gpu)
 
     explicit SkImage_Gpu(const SkBitmap&);
     virtual ~SkImage_Gpu();
 
-    virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) SK_OVERRIDE;
-    virtual void onDrawRectToRect(SkCanvas*, const SkRect* src, const SkRect& dst, const SkPaint*) SK_OVERRIDE;
-    virtual GrTexture* onGetTexture() SK_OVERRIDE;
+    virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) const SK_OVERRIDE;
+    virtual void onDrawRectToRect(SkCanvas*, const SkRect* src, const SkRect& dst,
+                                  const SkPaint*) const SK_OVERRIDE;
+    virtual GrTexture* onGetTexture() const SK_OVERRIDE;
     virtual bool getROPixels(SkBitmap*) const SK_OVERRIDE;
 
-    GrTexture* getTexture() { return fBitmap.getTexture(); }
+    GrTexture* getTexture() const { return fBitmap.getTexture(); }
 
     virtual SkShader* onNewShader(SkShader::TileMode,
                                   SkShader::TileMode,
                                   const SkMatrix* localMatrix) const SK_OVERRIDE;
 private:
     SkBitmap    fBitmap;
 
     typedef SkImage_Base INHERITED;
 };
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImage_Gpu::SkImage_Gpu(const SkBitmap& bitmap)
     : INHERITED(bitmap.width(), bitmap.height())
     , fBitmap(bitmap) {
     SkASSERT(NULL != fBitmap.getTexture());
 }
 
 SkImage_Gpu::~SkImage_Gpu() {
 }
 
 SkShader* SkImage_Gpu::onNewShader(SkShader::TileMode tileX,
                                    SkShader::TileMode tileY,
                                    const SkMatrix* localMatrix) const
 {
     return SkShader::CreateBitmapShader(fBitmap, tileX, tileY, localMatrix);
 }
 
-void SkImage_Gpu::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y,
-                         const SkPaint* paint) {
+void SkImage_Gpu::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y, const SkPaint* paint) const {
     canvas->drawBitmap(fBitmap, x, y, paint);
 }
 
 void SkImage_Gpu::onDrawRectToRect(SkCanvas* canvas, const SkRect* src, const SkRect& dst,
-                         const SkPaint* paint) {
+                                   const SkPaint* paint) const {
     canvas->drawBitmapRectToRect(fBitmap, src, dst, paint);
 }
 
-GrTexture* SkImage_Gpu::onGetTexture() {
+GrTexture* SkImage_Gpu::onGetTexture() const {
     return fBitmap.getTexture();
 }
 
 bool SkImage_Gpu::getROPixels(SkBitmap* dst) const {
     return fBitmap.copyTo(dst, kN32_SkColorType);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkImage* SkImage::NewTexture(const SkBitmap& bitmap) {
     if (NULL == bitmap.getTexture()) {
         return NULL;
     }
 
     return SkNEW_ARGS(SkImage_Gpu, (bitmap));
 }
 
 GrTexture* SkTextureImageGetTexture(SkImage* image) {
     return ((SkImage_Gpu*)image)->getTexture();
 }