Add needed virtual destructors.

These were found by the clang on Windows build.

R=mtklein@google.com

Author: bungeman@google.com

Review URL: https://codereview.chromium.org/328303005

src/ports/SkFontMgr_win_dw.cpp

@@ -46,6 +46,7 @@ public:
 
 private:
     StreamFontFileLoader(SkStream* stream) : fRefCount(1), fStream(SkRef(stream)) { }
+    virtual ~StreamFontFileLoader() { }
 
     ULONG fRefCount;
 };
@@ -107,6 +108,8 @@ public:
     }
 private:
     StreamFontFileEnumerator(IDWriteFactory* factory, IDWriteFontFileLoader* fontFileLoader);
+    virtual ~StreamFontFileEnumerator() { }
+
     ULONG fRefCount;
 
     SkTScopedComPtr<IDWriteFactory> fFactory;
@@ -205,6 +208,7 @@ private:
         : fRefCount(1)
         , fFontFileLoader(SkRefComPtr(fontFileLoader))
     { }
+    virtual ~StreamFontCollectionLoader() { }
 
     ULONG fRefCount;
     SkTScopedComPtr<IDWriteFontFileLoader> fFontFileLoader;

src/ports/SkRemotableFontMgr_win_dw.cpp

@@ -290,6 +290,8 @@ public:
           fIdentity.fDataId = SkFontIdentity::kInvalidDataId;
         }
 
+        virtual ~FontFallbackRenderer() { }
+
         // IDWriteTextRenderer methods
         virtual HRESULT STDMETHODCALLTYPE DrawGlyphRun(
             void* clientDrawingContext,

src/utils/win/SkDWriteFontFileStream.h

@@ -68,6 +68,7 @@ public:
 
 private:
     explicit SkDWriteFontFileStreamWrapper(SkStream* stream);
+    virtual ~SkDWriteFontFileStreamWrapper() { }
 
     ULONG fRefCount;
     SkAutoTUnref<SkStream> fStream;