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/TextDropShadowCache.h b/libs/hwui/TextDropShadowCache.h
index 54b930b..bb53a23 100644
--- a/libs/hwui/TextDropShadowCache.h
+++ b/libs/hwui/TextDropShadowCache.h
@@ -24,13 +24,14 @@
 #include <utils/LruCache.h>
 #include <utils/String16.h>
 
-#include "FontRenderer.h"
+#include "font/Font.h"
 #include "Texture.h"
 
 namespace android {
 namespace uirenderer {
 
 class Caches;
+class FontRenderer;
 
 struct ShadowText {
     ShadowText(): len(0), radius(0.0f), textSize(0.0f), typeface(NULL),