Implement a persistent uniqueID-based cache for SkImageFilter.

src/gpu/SkGpuDevice.cpp

Index: src/gpu/SkGpuDevice.cpp
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 0abf9d84b5588bc00597abd67e41dac949e01262..2853805a5b1b3bcbb73e461eb4a493d01756badb 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -41,6 +41,8 @@
 #include "SkXfermode.h"
 #include "SkErrorInternals.h"
 
+enum { kDefaultImageFilterCacheSize = 32 * 1024 * 1024 };
+
 #define CACHE_COMPATIBLE_DEVICE_TEXTURES 1
 
 #if 0
@@ -1425,8 +1427,9 @@ void SkGpuDevice::drawSprite(const SkDraw& draw, const SkBitmap& bitmap,
         SkMatrix matrix(*draw.fMatrix);
         matrix.postTranslate(SkIntToScalar(-left), SkIntToScalar(-top));
         SkIRect clipBounds = SkIRect::MakeWH(bitmap.width(), bitmap.height());
-        SkImageFilter::Cache* cache = SkImageFilter::Cache::Create();
-        SkAutoUnref aur(cache);
+        SkAutoTUnref<SkImageFilter::UniqueIDCache> cache(getImageFilterCache());
+        // This cache is transient, and is freed (along with all its contained
+        // textures) when it goes out of scope.
         SkImageFilter::Context ctx(matrix, clipBounds, cache);
         if (filter_texture(this, fContext, texture, filter, w, h, ctx, &filteredBitmap,
                            &offset)) {
@@ -1535,8 +1538,9 @@ void SkGpuDevice::drawDevice(const SkDraw& draw, SkBaseDevice* device,
         SkMatrix matrix(*draw.fMatrix);
         matrix.postTranslate(SkIntToScalar(-x), SkIntToScalar(-y));
         SkIRect clipBounds = SkIRect::MakeWH(devTex->width(), devTex->height());
-        SkImageFilter::Cache* cache = SkImageFilter::Cache::Create();
-        SkAutoUnref aur(cache);
+        // This cache is transient, and is freed (along with all its contained
+        // textures) when it goes out of scope.
+        SkAutoTUnref<SkImageFilter::UniqueIDCache> cache(getImageFilterCache());
         SkImageFilter::Context ctx(matrix, clipBounds, cache);
         if (filter_texture(this, fContext, devTex, filter, w, h, ctx, &filteredBitmap,
                            &offset)) {
@@ -2060,3 +2064,9 @@ bool SkGpuDevice::EXPERIMENTAL_drawPicture(SkCanvas* canvas, const SkPicture* pi
 
     return true;
 }
+
+SkImageFilter::UniqueIDCache* SkGpuDevice::getImageFilterCache() {
+    // We always return a transient cache, so it is freed after each
+    // filter traversal.
+    return SkImageFilter::UniqueIDCache::Create(kDefaultImageFilterCacheSize);
+}