Round the snapped position when checking snapped

so that it can handle negative errors (like 0.999)

BUG=None
R=danakj@chromium.org

Review URL: https://codereview.chromium.org/467813002

Cr-Commit-Position: refs/heads/master@{#289105}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289105 0039d316-1c4b-4281-b951-d872f2087c98

ui/compositor/dip_util.cc

@@ -81,7 +81,7 @@ namespace {
 
 void CheckSnapped(float snapped_position) {
   const float kEplison = 0.0001f;
-  float diff = std::abs(snapped_position - static_cast<int>(snapped_position));
+  float diff = std::abs(snapped_position - gfx::ToRoundedInt(snapped_position));
   DCHECK_LT(diff, kEplison);
 }