Fix narrowing warning error

tests/JpegTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkData.h"
 #include "SkForceLinking.h"
 #include "SkImageDecoder.h"
 #include "SkImage.h"
 #include "SkStream.h"
 #include "Test.h"
 
 __SK_FORCE_IMAGE_DECODER_LINKING;
 
 #define JPEG_TEST_WRITE_TO_FILE_FOR_DEBUGGING 0  // do not do this for
                                                  // normal unit testing.
 
 namespace {
-    char goodJpegImage[] = {
+    unsigned char goodJpegImage[] = {
         0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10, 0x4A, 0x46,
         0x49, 0x46, 0x00, 0x01, 0x01, 0x01, 0x00, 0x8F,
         0x00, 0x8F, 0x00, 0x00, 0xFF, 0xDB, 0x00, 0x43,
         0x00, 0x05, 0x03, 0x04, 0x04, 0x04, 0x03, 0x05,
         0x04, 0x04, 0x04, 0x05, 0x05, 0x05, 0x06, 0x07,
         0x0C, 0x08, 0x07, 0x07, 0x07, 0x07, 0x0F, 0x0B,
         0x0B, 0x09, 0x0C, 0x11, 0x0F, 0x12, 0x12, 0x11,
         0x0F, 0x11, 0x11, 0x13, 0x16, 0x1C, 0x17, 0x13,
         0x14, 0x1A, 0x15, 0x11, 0x11, 0x18, 0x21, 0x18,
         0x1A, 0x1D, 0x1D, 0x1F, 0x1F, 0x1F, 0x13, 0x17,
@@ skipping 414 matching lines @@
     // Check to see that the resulting bitmap is nice
     bool writeSuccess = (!(bm8888.empty())) && SkImageEncoder::EncodeFile(
         "HalfOfAJpeg.png", bm8888, SkImageEncoder::kPNG_Type, 100);
     SkASSERT(writeSuccess);
     #endif
 }
 
 #include "TestClassDef.h"
 DEFINE_TESTCLASS("JpegTest", JpegTestClass, TestJpeg)