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.cpp b/libs/hwui/OpenGLRenderer.cpp
index 71836dd5..cd09f86 100644
--- a/libs/hwui/OpenGLRenderer.cpp
+++ b/libs/hwui/OpenGLRenderer.cpp
@@ -2042,10 +2042,10 @@
     return DrawGlInfo::kStatusDrew;
 }
 
-status_t OpenGLRenderer::drawBitmap(const SkBitmap* bitmap, const SkMatrix* matrix,
+status_t OpenGLRenderer::drawBitmap(const SkBitmap* bitmap, const SkMatrix& matrix,
         const SkPaint* paint) {
     Rect r(0.0f, 0.0f, bitmap->width(), bitmap->height());
-    const mat4 transform(*matrix);
+    const mat4 transform(matrix);
     transform.mapRect(r);
 
     if (quickRejectSetupScissor(r.left, r.top, r.right, r.bottom)) {