Make mapLocalToContainer() work properly for content that follows a column spanner.

LayoutTests/fast/multicol/client-rect-after-spanner-expected.txt

Index: LayoutTests/fast/multicol/client-rect-after-spanner-expected.txt
diff --git a/LayoutTests/fast/multicol/client-rect-after-spanner-expected.txt b/LayoutTests/fast/multicol/client-rect-after-spanner-expected.txt
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index 0000000000000000000000000000000000000000..31b996a0ae513ba044f2e803acecf6cf4d8a059a
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+++ b/LayoutTests/fast/multicol/client-rect-after-spanner-expected.txt
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+Test that getBoundingClientRect works as expected on content after a spanner.
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+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
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+PASS document.getElementById('elm1').getBoundingClientRect().left is 100
+PASS document.getElementById('elm1').getBoundingClientRect().top is 220
+PASS document.getElementById('elm2').getBoundingClientRect().left is 100
+PASS document.getElementById('elm2').getBoundingClientRect().top is 270
+PASS document.getElementById('elm3').getBoundingClientRect().left is 216
+PASS document.getElementById('elm3').getBoundingClientRect().top is 220
+PASS document.getElementById('elm4').getBoundingClientRect().left is 216
+PASS document.getElementById('elm4').getBoundingClientRect().top is 270
+PASS document.getElementById('elm5').getBoundingClientRect().left is 332
+PASS document.getElementById('elm5').getBoundingClientRect().top is 220
+PASS successfullyParsed is true
+
+TEST COMPLETE
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