Add SkWebpCodec, for decoding .webp images.

tests/CodexTest.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Resources.h"
 #include "SkBitmap.h"
 #include "SkCodec.h"
@@ skipping 71 matching lines @@
         REPORTER_ASSERT(r, digest3 == digest1);
     } else {
         REPORTER_ASSERT(r, !scanlineDecoder);
     }
 }
 
 DEF_TEST(Codec, r) {
     // WBMP
     check(r, "mandrill.wbmp", SkISize::Make(512, 512), false);
 
+    // WEBP
+    check(r, "baby_tux.webp", SkISize::Make(386, 395), false);
+    check(r, "color_wheel.webp", SkISize::Make(128, 128), false);
+    check(r, "yellow_rose.webp", SkISize::Make(400, 301), false);
+
     // BMP
     check(r, "randPixels.bmp", SkISize::Make(8, 8), false);
 
     // ICO
     // These two tests examine interestingly different behavior:
     // Decodes an embedded BMP image
     check(r, "color_wheel.ico", SkISize::Make(128, 128), false);
     // Decodes an embedded PNG image
     check(r, "google_chrome.ico", SkISize::Make(256, 256), false);
 
@@ skipping 110 matching lines @@
     test_empty(r, "empty_images/zero-embedded.ico");
     test_empty(r, "empty_images/zero-width.bmp");
     test_empty(r, "empty_images/zero-height.bmp");
     test_empty(r, "empty_images/zero-width.jpg");
     test_empty(r, "empty_images/zero-height.jpg");
     test_empty(r, "empty_images/zero-width.png");
     test_empty(r, "empty_images/zero-height.png");
     test_empty(r, "empty_images/zero-width.wbmp");
     test_empty(r, "empty_images/zero-height.wbmp");
 }