Update HWUI matrix API

1. more closely mirror Skia API by using const ref instead of ptrs
2. store SkMatrix in the drawOp instead of the linear allocation heap

Change-Id: I4b9f6f76b9f7d19325e29303d27b793679fd4823
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index fc27947..0f953a5 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -170,7 +170,7 @@
             const SkPaint* paint);
     status_t drawBitmaps(const SkBitmap* bitmap, AssetAtlas::Entry* entry, int bitmapCount,
             TextureVertex* vertices, bool pureTranslate, const Rect& bounds, const SkPaint* paint);
-    virtual status_t drawBitmap(const SkBitmap* bitmap, const SkMatrix* matrix,
+    virtual status_t drawBitmap(const SkBitmap* bitmap, const SkMatrix& matrix,
             const SkPaint* paint);
     virtual status_t drawBitmap(const SkBitmap* bitmap, float srcLeft, float srcTop,
             float srcRight, float srcBottom, float dstLeft, float dstTop,