Return cropBitmap

cropBitmap returns 'true' on success and 'false' on failure.
Propagate its return value so that cascading failures can be avoided.

Signed-off-by: Mykola Kondratenko <mykola.kondratenko@sonymobile.com>

BUG=skia:

Review URL: https://codereview.chromium.org/1088093003
diff --git a/src/images/SkImageDecoder_libwebp.cpp b/src/images/SkImageDecoder_libwebp.cpp
index decccd1..a7c9610 100644
--- a/src/images/SkImageDecoder_libwebp.cpp
+++ b/src/images/SkImageDecoder_libwebp.cpp
@@ -395,8 +395,8 @@
     }
 
     if (!directDecode) {
-        cropBitmap(decodedBitmap, bitmap, sampleSize, region.x(), region.y(),
-                   region.width(), region.height(), rect.x(), rect.y());
+        return cropBitmap(decodedBitmap, bitmap, sampleSize, region.x(), region.y(),
+                          region.width(), region.height(), rect.x(), rect.y());
     }
     return true;
 }