Change SkImageDecoders to take an SkStreamRewindable.

src/utils/win/SkIStream.cpp

Index: src/utils/win/SkIStream.cpp
diff --git a/src/utils/win/SkIStream.cpp b/src/utils/win/SkIStream.cpp
index 7880fa0790c3251ca64e9963db6c4ca8e44f0185..182d9a8caab1bd6594ef36727194e4b8db0b1739 100644
--- a/src/utils/win/SkIStream.cpp
+++ b/src/utils/win/SkIStream.cpp
@@ -176,6 +176,8 @@ HRESULT STDMETHODCALLTYPE SkIStream::Seek(LARGE_INTEGER liDistanceToMove
         if (!this->fSkStream->rewind()) {
             hr = E_FAIL;
         } else {
+            // FIXME: Should not depend on getLength.
+            // See https://code.google.com/p/skia/issues/detail?id=1570
             LONGLONG skip = this->fSkStream->getLength()
                           + liDistanceToMove.QuadPart;
             size_t skipped = this->fSkStream->skip(static_cast<size_t>(skip));
@@ -204,6 +206,8 @@ HRESULT STDMETHODCALLTYPE SkIStream::Stat(STATSTG* pStatstg
         return STG_E_INVALIDFLAG;
     }
     pStatstg->pwcsName = NULL;
+    // FIXME: Should not depend on getLength
+    // See https://code.google.com/p/skia/issues/detail?id=1570
     pStatstg->cbSize.QuadPart = this->fSkStream->getLength();
     pStatstg->clsid = CLSID_NULL;
     pStatstg->type = STGTY_STREAM;