IWYU for some more test files starting with 'C'.

Change-Id: I010527b342cbfa0b425ef0d00966219413d9e77d
Reviewed-on: https://skia-review.googlesource.com/121886
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/tests/ColorMatrixTest.cpp b/tests/ColorMatrixTest.cpp
index baef520..8c25669 100644
--- a/tests/ColorMatrixTest.cpp
+++ b/tests/ColorMatrixTest.cpp
@@ -5,15 +5,17 @@
  * found in the LICENSE file.
  */
 
-#include "Test.h"
-
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkColor.h"
-#include "SkColorMatrixFilter.h"
+#include "SkColorFilter.h"
 #include "SkPaint.h"
+#include "SkRefCnt.h"
+#include "SkScalar.h"
+#include "Test.h"
 
-#include <stdlib.h>
+#include <cmath>
+#include <cstdlib>
 
 static inline void assert_color(skiatest::Reporter* reporter,
                                 SkColor expected, SkColor actual, int tolerance) {