Clean up physical coupling

Narrow the use of #include directives in hwui, replacing with forward
declarations where straightforward. Speeds compiles; doesn't do any
restructuring of code.

Change-Id: Icac2baffb5896f55d8c6718e9bd9d4bfa02d3ca0
diff --git a/libs/hwui/Caches.cpp b/libs/hwui/Caches.cpp
index f0bf7b2..478a3ec 100644
--- a/libs/hwui/Caches.cpp
+++ b/libs/hwui/Caches.cpp
@@ -21,6 +21,7 @@
 
 #include "Caches.h"
 #include "DisplayListRenderer.h"
+#include "GammaFontRenderer.h"
 #include "Properties.h"
 #include "LayerRenderer.h"
 #include "ShadowTessellator.h"