Make SkPngCodec decode progressively.

tests/ColorSpaceTest.cpp

 /*
  * Copyright 2016 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 "SkCodec.h"
 #include "SkColorSpace.h"
@@ skipping 49 matching lines @@
 }
 
 DEF_TEST(ColorSpaceParsePngICCProfile, r) {
     SkAutoTDelete<SkStream> stream(resource("color_wheel_with_profile.png"));
     REPORTER_ASSERT(r, nullptr != stream);
     if (!stream) {
         return;
     }
 
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream.release()));
-    REPORTER_ASSERT(r, nullptr != codec);
+    if (!codec) {
+        ERRORF(r, "Failed to create codec from a PNG. Is PNG support missing (or too old)?");
+        return;
+    }
 
 #if (PNG_LIBPNG_VER_MAJOR > 1) || (PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR >= 6)
     SkColorSpace* colorSpace = codec->getColorSpace();
     REPORTER_ASSERT(r, nullptr != colorSpace);
 
     test_space(r, colorSpace, &g_sRGB_XYZ[0], &g_sRGB_XYZ[3], &g_sRGB_XYZ[6], g_sRGB_gamma);
 #endif
 }
 
 DEF_TEST(ColorSpaceParseJpegICCProfile, r) {
@@ skipping 50 matching lines @@
         return;
     }
     sk_sp<SkColorSpace> monitorSpace = SkColorSpace::NewICC(monitorData->data(),
                                                             monitorData->size());
     sk_sp<SkData> newMonitorData = as_CSB(monitorSpace)->writeToICC();
     sk_sp<SkColorSpace> newMonitorSpace = SkColorSpace::NewICC(newMonitorData->data(),
                                                                newMonitorData->size());
     REPORTER_ASSERT(r, monitorSpace->xyz() == newMonitorSpace->xyz());
     REPORTER_ASSERT(r, as_CSB(monitorSpace)->gammas() == as_CSB(newMonitorSpace)->gammas());
 }