Simpler way to deal with the FBO multi-cache.

This change removes the need for the SortedList and instead just
add a generated id to each FBO stored in the cache. This is an
artificial way to store several FBOs with the same dimensions.

Change-Id: I9638364e9bdc0f2391261937a0c86096f20505bf
diff --git a/libs/hwui/LayerCache.cpp b/libs/hwui/LayerCache.cpp
index 7d85e7b..882ad83 100644
--- a/libs/hwui/LayerCache.cpp
+++ b/libs/hwui/LayerCache.cpp
@@ -28,8 +28,8 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 LayerCache::LayerCache(uint32_t maxByteSize):
-        mCache(GenerationMultiCache<LayerSize, Layer*>::kUnlimitedCapacity),
-        mSize(0), mMaxSize(maxByteSize) {
+        mCache(GenerationCache<LayerSize, Layer*>::kUnlimitedCapacity),
+        mIdGenerator(1), mSize(0), mMaxSize(maxByteSize) {
 }
 
 LayerCache::~LayerCache() {
@@ -101,6 +101,7 @@
             deleteLayer(oldest);
         }
 
+        layerSize.id = mIdGenerator++;
         mCache.put(layerSize, layer);
         mSize += size;