Retract GrTexture*.h & GrRenderTarget*.h from other headers

This does push some additional work (& includes) into the .cpp files.

Change-Id: I27c847e371802270d13594dcc22aae44039990bb
Reviewed-on: https://skia-review.googlesource.com/19660
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/tests/ImageFilterCacheTest.cpp b/tests/ImageFilterCacheTest.cpp
index d0c6c5b..2334172 100644
--- a/tests/ImageFilterCacheTest.cpp
+++ b/tests/ImageFilterCacheTest.cpp
@@ -182,6 +182,7 @@
 #include "GrContextPriv.h"
 #include "GrResourceProvider.h"
 #include "GrTest.h"
+#include "GrTexture.h"
 
 static sk_sp<GrTextureProxy> create_proxy(GrResourceProvider* resourceProvider) {
     SkBitmap srcBM = create_bm();