Adds a mechanism for GrCacheable objects to notify the resource cache
when their size has changed. GrResourceCacheEntry now holds a
reference to the cache, and a cached value of the resource's most
recent size.

Also utilizes this new functionality for mipmaps, and adds a test for
changing resource sizes.

R=bsalomon@google.com, robertphillips@google.com

Author: cdalton@nvidia.com

Review URL: https://codereview.chromium.org/257093002

git-svn-id: http://skia.googlecode.com/svn/trunk@14576 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/GrCacheable.h b/include/gpu/GrCacheable.h
index 75dec16..39c62b1 100644
--- a/include/gpu/GrCacheable.h
+++ b/include/gpu/GrCacheable.h
@@ -46,6 +46,14 @@
 
     bool isInCache() const { return NULL != fCacheEntry; }
 
+    /**
+     * This entry point should be called whenever gpuMemorySize() begins
+     * reporting a different size. If the object is in the cache, it will call
+     * gpuMemorySize() immediately and pass the new size on to the resource
+     * cache.
+     */
+    void didChangeGpuMemorySize() const;
+
 private:
     GrResourceCacheEntry* fCacheEntry;  // NULL if not in cache