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/TreeInfo.h b/libs/hwui/TreeInfo.h
index ae6ea94..e820b22 100644
--- a/libs/hwui/TreeInfo.h
+++ b/libs/hwui/TreeInfo.h
@@ -20,7 +20,6 @@
 
 #include <utils/Timers.h>
 
-#include "DamageAccumulator.h"
 #include "utils/Macros.h"
 
 namespace android {
@@ -30,6 +29,7 @@
 class CanvasContext;
 }
 
+class DamageAccumulator;
 class OpenGLRenderer;
 class RenderState;