Add tile rendering to GM

This change is necessary to reproducing the SkPictureRecord/impl-side painting bug (it is the re-rendering of the same picture at multiple locations that triggers the bug). It cannot be enabled yet due several rendering issues but I would like to deliver it so others can experiment and debug.

[bsalomon, 2013-04-01 17:36:43]

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp
File gm/gmmain.cpp (right):

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp#newcode453
gm/gmmain.cpp:453: bitmap_copy_subset(tileBM, bitmap,
Maybe create an SkCanvas around bitmap and drawBitmap(tileBM) to it?

[robertphillips, 2013-04-01 18:21:51]

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp
File gm/gmmain.cpp (right):

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp#newcode453
gm/gmmain.cpp:453: bitmap_copy_subset(tileBM, bitmap,
What does that buy us?

[bsalomon, 2013-04-01 18:28:25]

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp
File gm/gmmain.cpp (right):

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp#newcode453
gm/gmmain.cpp:453: bitmap_copy_subset(tileBM, bitmap,
On 2013/04/01 18:21:52, robertphillips wrote:
> What does that buy us?

Faster, works with different src/dst bitmap types, fewer lines of code, maybe
easier to read

// three lines of setup
SkCanvas bmpCanvas(*bitmap);
SkPaint bmpPaint;
bmpPaint.setXfermodeMode(SkXfermode::kSrc_Mode);

// one to draw.
bmpCanvas.drawBitmap(tileBmp, xTile * tileSize.width(), yTile *
tileSize.height(), &bmpPaint);

[robertphillips, 2013-04-02 13:29:53]

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp
File gm/gmmain.cpp (right):

https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp#newcode453
gm/gmmain.cpp:453: bitmap_copy_subset(tileBM, bitmap,
On 2013/04/01 18:28:27, bsalomon wrote:
> On 2013/04/01 18:21:52, robertphillips wrote:
> > What does that buy us?
> 
> Faster, works with different src/dst bitmap types, fewer lines of code, maybe
> easier to read
> 
> // three lines of setup
> SkCanvas bmpCanvas(*bitmap);
> SkPaint bmpPaint;
> bmpPaint.setXfermodeMode(SkXfermode::kSrc_Mode);
> 
> // one to draw.
> bmpCanvas.drawBitmap(tileBmp, xTile * tileSize.width(), yTile *
> tileSize.height(), &bmpPaint);
> 
>     

Done.

[bsalomon, 2013-04-02 14:49:04]

On 2013/04/02 13:29:53, robertphillips wrote:
> https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp
> File gm/gmmain.cpp (right):
> 
> https://codereview.chromium.org/13165011/diff/1/gm/gmmain.cpp#newcode453
> gm/gmmain.cpp:453: bitmap_copy_subset(tileBM, bitmap,
> On 2013/04/01 18:28:27, bsalomon wrote:
> > On 2013/04/01 18:21:52, robertphillips wrote:
> > > What does that buy us?
> > 
> > Faster, works with different src/dst bitmap types, fewer lines of code,
maybe
> > easier to read
> > 
> > // three lines of setup
> > SkCanvas bmpCanvas(*bitmap);
> > SkPaint bmpPaint;
> > bmpPaint.setXfermodeMode(SkXfermode::kSrc_Mode);
> > 
> > // one to draw.
> > bmpCanvas.drawBitmap(tileBmp, xTile * tileSize.width(), yTile *
> > tileSize.height(), &bmpPaint);
> > 
> >     
> 
> Done.

lgtm

[robertphillips, 2013-04-02 15:19:00]

committed as r8485