separate c headers

BUG=skia:

Review URL: https://codereview.chromium.org/728323002
diff --git a/tests/CTest.cpp b/tests/CTest.cpp
index f663dcf..8127e9b 100644
--- a/tests/CTest.cpp
+++ b/tests/CTest.cpp
@@ -5,7 +5,10 @@
  * found in the LICENSE file.
  */
 
+#include "sk_canvas.h"
+#include "sk_paint.h"
 #include "sk_surface.h"
+
 #include "Test.h"
 
 static void test_c(skiatest::Reporter* reporter) {