Implement SkPicture::bytesUsed() for SkRecord backend

src/core/SkTileGrid.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTileGrid.h"
 
 SkTileGrid::SkTileGrid(int xTiles, int yTiles, const SkTileGridFactory::TileGridInfo& info)
@@ skipping 157 matching lines @@
         // We did find an earliest op. Output it, and step forward every tile that contains it.
         results->push(earliest);
         for (int i = 0; i < starts.count(); i++) {
             if (starts[i] < ends[i] && *starts[i] == earliest) {
                 starts[i]++;
             }
         }
     }
 }
 
+size_t SkTileGrid::bytesUsed() const {
+    size_t byteCount = sizeof(SkTileGrid);
+
+    for (int i = 0; i < fXTiles * fYTiles; i++) {

[chrishtr, 2014/11/17 21:34:21]

Will this be slow? Overall, what asymptotic runtime should we expect for the
public bytesUsed() method?

[tomhudson, 2014/11/17 22:12:15]

If the tile grid just spans a screen on the Nexus 9, it'd be 8x6, so ~50 adds
and multiplies, but there should be a buffer above and below the screen. If
that's 2kpx each way we're looking at 24x6 -> 150 adds and multiplies?

If it's expensive in practice, I suspect it'll be much more reasonable to cache
than to try to track as we go, but either ought to be feasible.

+        byteCount = fTiles[i].reserved() * sizeof(unsigned);

[mtklein, 2014/11/17 23:15:33]

I think you want += here?

While you're at it, can't hurt to move the multiply out of the loop.

+    }
+
+    return byteCount;
+}