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/Animator.cpp b/libs/hwui/Animator.cpp
index 8bf2107..a1bbc06 100644
--- a/libs/hwui/Animator.cpp
+++ b/libs/hwui/Animator.cpp
@@ -20,6 +20,7 @@
 #include <set>
 
 #include "AnimationContext.h"
+#include "Interpolator.h"
 #include "RenderNode.h"
 #include "RenderProperties.h"