Cleanup resourceless_software_draw()

content/browser/android/in_process/synchronous_compositor_output_surface.cc

Index: content/browser/android/in_process/synchronous_compositor_output_surface.cc
diff --git a/content/browser/android/in_process/synchronous_compositor_output_surface.cc b/content/browser/android/in_process/synchronous_compositor_output_surface.cc
index 682c530dc3938d61d0557ddb5e439a1998102c00..b8d4c5ffb313562be4f6987d2d15276f11f1ddfa 100644
--- a/content/browser/android/in_process/synchronous_compositor_output_surface.cc
+++ b/content/browser/android/in_process/synchronous_compositor_output_surface.cc
@@ -200,7 +200,7 @@ SynchronousCompositorOutputSurface::DemandDrawSw(SkCanvas* canvas) {
   surface_size_ = gfx::Size(canvas->getDeviceSize().width(),
                             canvas->getDeviceSize().height());
 
-  // Resourceless software draw does not need viewport_for_tiling.
+  // Resourceless software draw does not need viewport_rect_for_tile_priority.
   gfx::Rect empty;
   InvokeComposite(transform, clip, clip, empty, gfx::Transform(), false);

[boliu, 2014/08/29 00:36:11]

wait wot? Of course you need it, used the cached version.

[hush (inactive), 2014/08/29 00:50:55]

Maybe that comment is not clear enough... That comment refers to "empty" rect
passed in for viewport_rect_for_tile_priority, because empty rect is used for
the resourceless software draw.

The cached version is used after the software draw. 
On 2014/08/29 00:36:11, boliu wrote:

[boliu, 2014/08/29 00:56:32]

It's clear and it's wrong.

The viewport/matrix for tile priority must be correct (ie match the ones used in
hardware draw) at all times. Otherwise you can get widely different tiling
priorities between software and hardware draws, causing tiles to thrash.

This refactor was only possible after we separated out draw viewport and the
tile viewport. cc used to ignore tile viewport/matrix and use the old value if
it's a software draw. Now we have the old value right here, so just pass the old
values in, so no need for cc to special case software draws.

[hush (inactive), 2014/08/29 01:29:51]

Cool. I see. Uploaded another patch for it.
On 2014/08/29 00:56:32, boliu wrote: