C API: Add SK_API, also documentation of an example.

tests/CTest.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
+#include "Test.h"
+
 #include "sk_canvas.h"
 #include "sk_paint.h"
 #include "sk_surface.h"
 #include "sk_shader.h"
 
-#include "Test.h"
-
-
 static void shader_test(skiatest::Reporter* reporter) {
     sk_imageinfo_t info =
         {64, 64, sk_colortype_get_default_8888(), PREMUL_SK_ALPHATYPE};
     sk_surface_t* surface  = sk_surface_new_raster(&info, nullptr);
     sk_canvas_t* canvas = sk_surface_get_canvas(surface);
     sk_paint_t* paint = sk_paint_new();
 
     sk_shader_tilemode_t tilemode = CLAMP_SK_SHADER_TILEMODE;
     sk_point_t point = {0.0f, 0.0f};
     sk_point_t point2 = {30.0f, 40.0f};
@@ skipping 54 matching lines @@
     REPORTER_ASSERT(reporter, 0x80404040 == pixel[0]);
 
     sk_paint_delete(paint);
     sk_surface_unref(surface);
 }
 
 DEF_TEST(C_API, reporter) {
     test_c(reporter);
     shader_test(reporter);
 }