cc: Change damage tracking from floats to integers.

Damage rects can become huge when layers clip the viewport, and in some
cases become so large that we reach inaccurate floating point
representation of the whole-number portion, which we fail to handle
correctly when doing gfx::ToEnclosingRect.

Int/float conversions are also slow, and the GL_SCISSOR wants integers
eventually anyway, so keeping track of partial-pixel damage is not
buying us much here. So convert the DamageTracker to use integer rects.

Also change cc::RenderSurfaceImpl to export a damage_rect that is
contained inside the output_rect for the RenderPass, and add DCHECKs
to cc::RenderPass to ensure we don't send pointlessly large damage_rects
to the cc::Renderer.

Tests:
DamageTrackerTest.HugeDamageRect

R=enne@chromium.org, piman@chromium.org
BUG=355514

Review URL: https://codereview.chromium.org/226183007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@262160 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 2 insertions, 1 deletions

diff --git a/cc/layers/render_surface_impl.cc b/cc/layers/render_surface_impl.cc
index ddb7158..fa7dcb8 100644
--- a/cc/layers/render_surface_impl.cc
+++ b/cc/layers/render_surface_impl.cc
@@ -130,7 +130,8 @@ void RenderSurfaceImpl::AppendRenderPasses(RenderPassSink* pass_sink) {
   scoped_ptr<RenderPass> pass = RenderPass::Create(layer_list_.size());
   pass->SetNew(RenderPassId(),
                content_rect_,
-               damage_tracker_->current_damage_rect(),
+               gfx::IntersectRects(content_rect_,
+                                   damage_tracker_->current_damage_rect()),
                screen_space_transform_);
   pass_sink->AppendRenderPass(pass.Pass());
 }