wip for drawables

Idea:

1. in its mutable recording state, keep a table of drawables on the side, and store an index in the record list.

2. In "immediate-mode" draw, just call the clients drawable directly (need access to our private list to turn the stored index into a proc)

3. when we "snap", we replace the list of drawables with a list of (sub) pictures, and then during playback of the snapped picture, we invoke a private drawable which just calls "drawPicture" on the index'd subpicture.

Review URL: https://codereview.chromium.org/727363003
diff --git a/tools/DumpRecord.cpp b/tools/DumpRecord.cpp
index c505123..2d05516 100644
--- a/tools/DumpRecord.cpp
+++ b/tools/DumpRecord.cpp
@@ -21,7 +21,7 @@
         : fDigits(0)
         , fIndent(0)
         , fIndex(0)
-        , fDraw(canvas)
+        , fDraw(canvas, NULL, 0, NULL)
         , fTimeWithCommand(timeWithCommand) {
         while (count > 0) {
             count /= 10;