When bitmap is texture backed, don't download and reupload pixels

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 "GrDrawTargetCaps.h"
@@ skipping 342 matching lines @@
     }
     SkAutoLockPixels alp(*bitmap);
     if (!bitmap->readyToDraw()) {
         return NULL;
     }
 
     return sk_gr_allocate_texture(ctx, cache, params, origBitmap, desc,
                                   bitmap->getPixels(), bitmap->rowBytes());
 }
 
+static GrTexture* get_texture_backing_bmp(const SkBitmap& bitmap, const GrContext* context,
+                                          const GrTextureParams* params) {
+    if (GrTexture* texture = bitmap.getTexture()) {
+        // Our texture-resizing-for-tiling used to upscale NPOT textures for tiling only works with
+        // content-key cached resources. Rather than invest in that legacy code path, we'll just
+        // take the horribly slow route of causing a cache miss which will cause the pixels to be
+        // read and reuploaded to a texture with a content key.
+        if (params && !context->getGpu()->caps()->npotTextureTileSupport() &&
+            (params->isTiled() || GrTextureParams::kMipMap_FilterMode == params->filterMode())) {
+            return NULL;
+        }
+        return texture;
+    }
+    return NULL;
+}
+
 bool GrIsBitmapInCache(const GrContext* ctx,
                        const SkBitmap& bitmap,
                        const GrTextureParams* params) {
+    if (get_texture_backing_bmp(bitmap, ctx, params)) {
+        return true;
+    }
+
     GrCacheID cacheID;
     generate_bitmap_cache_id(bitmap, &cacheID);
 
     GrSurfaceDesc desc;
     generate_bitmap_texture_desc(bitmap, &desc);
     return ctx->isTextureInCache(desc, cacheID, params);
 }
 
 GrTexture* GrRefCachedBitmapTexture(GrContext* ctx,
                                     const SkBitmap& bitmap,
                                     const GrTextureParams* params) {
-    GrTexture* result = NULL;
+    GrTexture* result = get_texture_backing_bmp(bitmap, ctx, params);
+    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);
 
         GrSurfaceDesc desc;
@@ skipping 158 matching lines @@
         if (shader->asFragmentProcessor(context, skPaint, viewM, 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);
 }