don't leak the bitmap filter

src/core/SkBitmapProcState.h

Index: src/core/SkBitmapProcState.h
diff --git a/src/core/SkBitmapProcState.h b/src/core/SkBitmapProcState.h
index 1f75533410001b88d20a7ea9a83a9d379808e1f3..5c6a4152fc285dd9c92fedc65f8e727f8bb920dc 100644
--- a/src/core/SkBitmapProcState.h
+++ b/src/core/SkBitmapProcState.h
@@ -34,6 +34,11 @@ class SkPaint;
 
 struct SkBitmapProcState {
 
+    SkBitmapProcState(): fBitmapFilter(NULL) {}
+    ~SkBitmapProcState() {
+        SkDELETE(fBitmapFilter);
+    }
+
     typedef void (*ShaderProc32)(const SkBitmapProcState&, int x, int y,
                                  SkPMColor[], int count);