Retract GrRenderTarget from GrTestTarget

Split out of: https://codereview.chromium.org/1988923002/ (Declassify GrClipMaskManager and Remove GrRenderTarget and GrDrawTarget from GrPipelineBuilder)

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Review-Url: https://codereview.chromium.org/2004433002
diff --git a/bench/GLBench.cpp b/bench/GLBench.cpp
index 524bfe1..8cf41c2 100644
--- a/bench/GLBench.cpp
+++ b/bench/GLBench.cpp
@@ -8,7 +8,9 @@
 #include "GLBench.h"
 
 #if SK_SUPPORT_GPU
+#include "GrGpu.h"
 #include "GrTest.h"
+#include "gl/GrGLContext.h"
 #include <stdio.h>
 
 const GrGLContext* GLBench::getGLContext(SkCanvas* canvas) {