remove unused field from SkDrawIter

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index bc5e030430ac0b84e660afedfa8f43b70376ab1c..2564e3703303f9f8f84fc7f1e6a043adb0509676 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -320,7 +320,6 @@ class SkDrawIter : public SkDraw {
 public:
     SkDrawIter(SkCanvas* canvas) {
         canvas = canvas->canvasForDrawIter();
-        fCanvas = canvas;
         canvas->updateDeviceCMCache();
 
         fClipStack = canvas->fClipStack;
@@ -361,7 +360,6 @@ public:
     const SkPaint* getPaint() const { return fPaint; }
 
 private:
-    SkCanvas*       fCanvas;
     const DeviceCM* fCurrLayer;
     const SkPaint*  fPaint;     // May be null.