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/GradientCache.h b/libs/hwui/GradientCache.h
index 6a783b1..c94b6f0 100644
--- a/libs/hwui/GradientCache.h
+++ b/libs/hwui/GradientCache.h
@@ -25,11 +25,11 @@
 #include <utils/Mutex.h>
 #include <utils/Vector.h>
 
-#include "Texture.h"
-
 namespace android {
 namespace uirenderer {
 
+class Texture;
+
 struct GradientCacheEntry {
     GradientCacheEntry() {
         count = 0;