[LayoutNG] Fix crash for very long line with break-word

This patch fixes NGLineBreaker crash when handling a very long line. Because line breaker determines overflow by the position being larger than the available width, it cannot stop if the available width is |LayoutUnit::Max()|. This patch clamps the available width by |LayoutUnit::NearlyMax()| to prevent that. The `word-wrap: break-word` is not necessary to cause the failure, but it makes things worse by setting |ShapeResult| to |nullptr| when overflow occurs for the performance reason. This patch also changes |BreakText| to return whether the overflow occurred or not, rather than callers to determine it from the position. Doing so helps clearer communication with the callers. Bug: 961987 Change-Id: I17eb758aca8b9b6d3e2f328e5b1b49acb83c0a5e
web-platform-tests · May 17, 2019 · 15184fd · 15184fd
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commit 15184fd
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diff --git a/css/css-text/overflow-wrap/overflow-wrap-break-word-long-crash.html b/css/css-text/overflow-wrap/overflow-wrap-break-word-long-crash.html
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+<!DOCTYPE html>
+<title>CSS Text Test: very long line with `overflow-wrap: break-word` should not crash</title>
+<link rel="help" href="https://crbug.com/961987">
+<link rel="author" title="Koji Ishii" href="kojii@chromium.org">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<style>
+html, body {
+  margin: 0;
+}
+body {
+  overflow-wrap: break-word;
+  width: 2147483648px;
+}
+div {
+  /* Double the width in case CSS parser clamps the body width. */
+  width: 200%;
+}
+span {
+  border-left: 2147483648px solid;
+}
+</style>
+<body>
+  <div><span>x</span></div>
+<script>
+test(() => { document.body.offsetTop; });
+</script>
+</body>