Don't readback and reupload texture-backed bitmaps

src/gpu/SkGr.cpp

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGr.h"
 #include "SkColorFilter.h"
 #include "SkConfig8888.h"
@@ skipping 354 matching lines @@
     generate_bitmap_cache_id(bitmap, &cacheID);
 
     GrTextureDesc desc;
     generate_bitmap_texture_desc(bitmap, &desc);
     return ctx->isTextureInCache(desc, cacheID, params);
 }
 
 GrTexture* GrLockAndRefCachedBitmapTexture(GrContext* ctx,
                                            const SkBitmap& bitmap,
                                            const GrTextureParams* params) {
-    GrTexture* result = NULL;
+    GrTexture* result = bitmap.getTexture();
+    if (result) {
+        return SkRef(result);
+    }
 
     bool cache = !bitmap.isVolatile();
 
     if (cache) {
         // If the bitmap isn't changing try to find a cached copy first.
 
         GrCacheID cacheID;
         generate_bitmap_cache_id(bitmap, &cacheID);
 
         GrTextureDesc desc;
         generate_bitmap_texture_desc(bitmap, &desc);
 
         result = ctx->findAndRefTexture(desc, cacheID, params);
     }
     if (NULL == result) {
         result = sk_gr_create_bitmap_texture(ctx, cache, params, bitmap);
     }
     if (NULL == result) {
         GrPrintf("---- failed to create texture for cache [%d %d]\n",
                     bitmap.width(), bitmap.height());
     }
     return result;
 }
 
 void GrUnlockAndUnrefCachedBitmapTexture(GrTexture* texture) {
     SkASSERT(texture->getContext());
 
-    texture->getContext()->unlockScratchTexture(texture);
+    if (texture->getCacheEntry()) {
+        texture->getContext()->unlockScratchTexture(texture);
+    }
     texture->unref();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 // alphatype is ignore for now, but if GrPixelConfig is expanded to encompass
 // alpha info, that will be considered.
 GrPixelConfig SkImageInfo2GrPixelConfig(SkColorType ct, SkAlphaType) {
     switch (ct) {
         case kUnknown_SkColorType:
@@ skipping 163 matching lines @@
         if (shader->asFragmentProcessor(context, skPaint, NULL, &paintColor, &fp) && fp) {
             grPaint->addColorProcessor(fp)->unref();
             constantColor = false;
         }
     }
 
     // The grcolor is automatically set when calling asFragmentProcessor.
     // If the shader can be seen as an effect it returns true and adds its effect to the grpaint.
     SkPaint2GrPaintNoShader(context, skPaint, paintColor, constantColor, grPaint);
 }