Tolerate subpixel differences in checkPaintInvalidationVisualRect()

We snap visual rect to pixels differently in different paths, so ignore
the subpixel differences.

This fixes failure of VisualRectMappingTest.LayoutText on mac with patch
https://codereview.chromium.org/2595323003/#ps160001

BUG=646176

Review-Url: https://codereview.chromium.org/2605163002
Cr-Commit-Position: refs/heads/master@{#440915}

third_party/WebKit/Source/core/layout/VisualRectMappingTest.cpp

@@ -33,7 +33,7 @@ class VisualRectMappingTest : public RenderingTest {
       PaintLayer::mapRectInPaintInvalidationContainerToBacking(
           paintInvalidationContainer, rect);
     }
-    EXPECT_EQ(rect, object.visualRect());
+    EXPECT_EQ(enclosingIntRect(rect), enclosingIntRect(object.visualRect()));
   }
 };