IWYU for gms starting with 'b'.

Change-Id: I34ded4a4b9c4600eaf801eec121ca851e04a6c23
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/211586
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/gm/bug6643.cpp b/gm/bug6643.cpp
index 60a0bfe..42debb5 100644
--- a/gm/bug6643.cpp
+++ b/gm/bug6643.cpp
@@ -6,7 +6,15 @@
  */
 
 #include "gm/gm.h"
+#include "include/core/SkCanvas.h"
+#include "include/core/SkColor.h"
+#include "include/core/SkPaint.h"
+#include "include/core/SkPicture.h"
 #include "include/core/SkPictureRecorder.h"
+#include "include/core/SkRefCnt.h"
+#include "include/core/SkShader.h"
+#include "include/core/SkTileMode.h"
+#include "include/core/SkTypes.h"
 #include "include/effects/SkGradientShader.h"
 
 DEF_SIMPLE_GM(bug6643, canvas, 200, 200) {