fix build. tests/BitmapTest w/ nogpu

NOTRY=true
TBR=herb@google.com

Change-Id: I09d7bd262a805e109a0869a83dec05ae03cff747
Reviewed-on: https://skia-review.googlesource.com/5687
Reviewed-by: Hal Canary <halcanary@google.com>
diff --git a/tests/BitmapTest.cpp b/tests/BitmapTest.cpp
index 98b1ac4..9342d26 100644
--- a/tests/BitmapTest.cpp
+++ b/tests/BitmapTest.cpp
@@ -7,6 +7,7 @@
 
 #include "SkBitmap.h"
 #include "SkMallocPixelRef.h"
+#include "SkRandom.h"
 #include "Test.h"
 
 static void test_peekpixels(skiatest::Reporter* reporter) {