Fix SkIStream nits.

Fix comment, constness of one field, and delete already checks for NULL.

TBR=reed@google.com
Trivial change to debatably public api.

Review URL: https://codereview.chromium.org/868643003
diff --git a/include/utils/win/SkIStream.h b/include/utils/win/SkIStream.h
index e2c2b96..9e04b7e 100644
--- a/include/utils/win/SkIStream.h
+++ b/include/utils/win/SkIStream.h
@@ -75,12 +75,12 @@
 };
 
 /**
- * A minimal read-only IStream implementation which wraps an SkIStream.
+ * A minimal read-only IStream implementation which wraps an SkStream.
  */
 class SkIStream : public SkBaseIStream {
 private:
     SkStream *fSkStream;
-    bool fDeleteOnRelease;
+    const bool fDeleteOnRelease;
     ULARGE_INTEGER fLocation;
 
     SkIStream(SkStream* stream, bool fDeleteOnRelease);
diff --git a/src/utils/win/SkIStream.cpp b/src/utils/win/SkIStream.cpp
index 2e9510c..dc9d163 100644
--- a/src/utils/win/SkIStream.cpp
+++ b/src/utils/win/SkIStream.cpp
@@ -113,7 +113,7 @@
 }
 
 SkIStream::~SkIStream() {
-    if (this->fSkStream && fDeleteOnRelease) {
+    if (fDeleteOnRelease) {
         delete this->fSkStream;
     }
 }