Remove external SkImageFilter cache, and rename UniqueIDCache -> Cache.

src/core/SkBitmapDevice.cpp

Index: src/core/SkBitmapDevice.cpp
diff --git a/src/core/SkBitmapDevice.cpp b/src/core/SkBitmapDevice.cpp
index 8c92f71dceee7aacee32d684293abab260b937ba..5f205ce1e6eb1add6826b2a11c61bd894556a6dc 100644
--- a/src/core/SkBitmapDevice.cpp
+++ b/src/core/SkBitmapDevice.cpp
@@ -367,8 +367,8 @@ const void* SkBitmapDevice::peekPixels(SkImageInfo* info, size_t* rowBytes) {
     return NULL;
 }
 
-SkImageFilter::UniqueIDCache* SkBitmapDevice::getImageFilterCache() {
-    SkImageFilter::UniqueIDCache* cache = SkImageFilter::UniqueIDCache::Get();
+SkImageFilter::Cache* SkBitmapDevice::getImageFilterCache() {
+    SkImageFilter::Cache* cache = SkImageFilter::Cache::Get();
     cache->ref();
     return cache;
 }