[WIP] Add Context to SkDrawLooper.

include/effects/SkLayerDrawLooper.h

Index: include/effects/SkLayerDrawLooper.h
diff --git a/include/effects/SkLayerDrawLooper.h b/include/effects/SkLayerDrawLooper.h
index 6955192b53f2e6f9edeb94f49efd0858a8a73b2b..7821e1a8f595bf851db0eff943fa8a17125f9c71 100644
--- a/include/effects/SkLayerDrawLooper.h
+++ b/include/effects/SkLayerDrawLooper.h
@@ -103,8 +103,7 @@ public:
     SkPaint* addLayerOnTop(const LayerInfo&);
 
     // overrides from SkDrawLooper
-    virtual void init(SkCanvas*);
-    virtual bool next(SkCanvas*, SkPaint* paint);
+    virtual SkDrawLooper::DrawContext* init(SkCanvas*) const;
 
     SK_DEVELOPER_TO_STRING()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLayerDrawLooper)
@@ -113,6 +112,9 @@ protected:
     SkLayerDrawLooper(SkReadBuffer&);
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
+    virtual bool next_internal(SkCanvas*, SkPaint* paint,
+                               SkDrawLooper::DrawContext* context) const;
+
 private:
     struct Rec {
         Rec*    fNext;
@@ -124,7 +126,10 @@ private:
     int     fCount;
 
     // state-machine during the init/next cycle
-    Rec* fCurrRec;
+    struct SkLayerDrawLooperContext : public SkDrawLooper::DrawContext {
+        explicit SkLayerDrawLooperContext(const SkLayerDrawLooper* looper);
+        Rec* fCurrRec;
+    };
 
     static void ApplyInfo(SkPaint* dst, const SkPaint& src, const LayerInfo&);