Update code to use helper function for better readability/searching.

Review URL: https://codereview.chromium.org/12834012

git-svn-id: http://skia.googlecode.com/svn/trunk@8287 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/images/SkImageDecoder_libico.cpp b/src/images/SkImageDecoder_libico.cpp
index 14f575b..ffc59e0 100644
--- a/src/images/SkImageDecoder_libico.cpp
+++ b/src/images/SkImageDecoder_libico.cpp
@@ -75,7 +75,7 @@
 
 bool SkICOImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode)
 {
-    size_t length = stream->read(NULL, 0);
+    size_t length = stream->getLength();
     SkAutoMalloc autoMal(length);
     unsigned char* buf = (unsigned char*)autoMal.get();
     if (stream->read((void*)buf, length) != length) {