cc: Stop checking the result of GetInverse in OcclusionTracker.

We don't draw layers with non-invertible transforms, so this check is
a waste. Especially in the case where we don't even use the inverse
transform.

R=enne

Review URL: https://codereview.chromium.org/492953002

Cr-Commit-Position: refs/heads/master@{#291242}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291242 0039d316-1c4b-4281-b951-d872f2087c98

cc/trees/occlusion_tracker.cc

@@ -519,10 +519,6 @@ bool OcclusionTracker<LayerType>::Occluded(
     return false;
   }
 
-  gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
-  if (!draw_transform.GetInverse(&inverse_draw_transform))
-    return false;
-
   // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
   // partial pixels in the resulting Rect.
   Region unoccluded_region_in_target_surface =
@@ -555,8 +551,8 @@ gfx::Rect OcclusionTracker<LayerType>::UnoccludedContentRect(
   }
 
   gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
-  if (!draw_transform.GetInverse(&inverse_draw_transform))
-    return content_rect;
+  bool ok = draw_transform.GetInverse(&inverse_draw_transform);
+  DCHECK(ok);
 
   // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
   // partial pixels in the resulting Rect.
@@ -600,8 +596,8 @@ gfx::Rect OcclusionTracker<LayerType>::UnoccludedContributingSurfaceContentRect(
     return content_rect;
 
   gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
-  if (!draw_transform.GetInverse(&inverse_draw_transform))
-    return content_rect;
+  bool ok = draw_transform.GetInverse(&inverse_draw_transform);
+  DCHECK(ok);
 
   // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
   // partial pixels in the resulting Rect.