simplify code in SkRecords.h

   - use C++11 features ({} init, move constructors) to eliminate the need
     for explicit constructors
   - collapse RECORD0...RECORD8 into just one RECORD macro
   - explicitly tag record types instead of using member detectors.

Removing member detectors makes this code significantly less fragile.

This exposes a few places where we didn't really think through what to do
with SkDrawable.  I've marked them TODO for now.

BUG=skia:

Review URL: https://codereview.chromium.org/1360943003
diff --git a/src/core/SkRecordDraw.cpp b/src/core/SkRecordDraw.cpp
index 1a03348..12920da 100644
--- a/src/core/SkRecordDraw.cpp
+++ b/src/core/SkRecordDraw.cpp
@@ -116,7 +116,7 @@
 DRAW(DrawTextOnPath, drawTextOnPath(r.text, r.byteLength, r.path, &r.matrix, r.paint));
 DRAW(DrawAtlas, drawAtlas(r.atlas, r.xforms, r.texs, r.colors, r.count, r.mode, r.cull, r.paint));
 DRAW(DrawVertices, drawVertices(r.vmode, r.vertexCount, r.vertices, r.texs, r.colors,
-                                r.xmode.get(), r.indices, r.indexCount, r.paint));
+                                r.xmode, r.indices, r.indexCount, r.paint));
 #undef DRAW
 
 template <> void Draw::draw(const DrawDrawable& r) {