remove unnecessary bitmapdevice references

TBR=

Author: reed@google.com

Review URL: https://codereview.chromium.org/354143004
diff --git a/tests/GradientTest.cpp b/tests/GradientTest.cpp
index 3e40010..3b09f85 100644
--- a/tests/GradientTest.cpp
+++ b/tests/GradientTest.cpp
@@ -5,7 +5,7 @@
  * found in the LICENSE file.
  */
 
-#include "SkBitmapDevice.h"
+#include "SkCanvas.h"
 #include "SkColorShader.h"
 #include "SkEmptyShader.h"
 #include "SkGradientShader.h"