Add a transient image filter cache to SkImage::makeWithFilter & PDF

src/core/SkImageFilterCache.h

Index: src/core/SkImageFilterCache.h
diff --git a/src/core/SkImageFilterCache.h b/src/core/SkImageFilterCache.h
index 25079e194fc6b5d61ce05e64bf6ca6aba5ddc225..edc58b8196f74b27a0dda6496f9a6246bad3b188 100644
--- a/src/core/SkImageFilterCache.h
+++ b/src/core/SkImageFilterCache.h
@@ -48,6 +48,8 @@ struct SkImageFilterCacheKey {
 // (result, offset).
 class SkImageFilterCache : public SkRefCnt {
 public:
+    enum { kDefaultSize = 32 * 1024 * 1024 };

[Stephen White, 2016/09/21 15:47:04]

I support the idea of centralizing this, but calling it kDefaultSize
is a little misleading.

SkImageFilterCache::Get(), used by the raster path, returns a (persistent) 128MB
cache, and doesn't use this value (it's in the .cpp).

Maybe we should call this one kDefaultTransientSize or
kDefaultTransientCacheSize or something, to distinguish it from the persistent
cache size?

+
     virtual ~SkImageFilterCache() {}
     static SkImageFilterCache* Create(size_t maxBytes);
     static SkImageFilterCache* Get();