[Layout] bugfix: Update scrollable area after overflow recalc

Bug is: <container overflow:scroll> <target transform:scale(1)> Initially, container's scrollbars are disabled. When target changes its scale and grows outside of container, scrollbars were not updated. Fix #1 is to call UpdateScrollbarEnabledState. This resulted in scrollbars being painted, but not clickable. Fix #2, calling UpdateScrollableAreaSet makes scrollbars clickable too. Fix #2 was an educated guess. Bug: 926167 Change-Id: I02454047c87aaecede9c56db1c02bbd1b21b15c5 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704218 Commit-Queue: Aleks Totic <atotic@chromium.org> Reviewed-by: Stefan Zager <szager@chromium.org> Cr-Commit-Position: refs/heads/master@{#681091}
bocoup · Jul 26, 2019 · a00fc08 · a00fc08
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diff --git a/css/css-scrollbars/scrollbars-chrome-bug-001-ref.html b/css/css-scrollbars/scrollbars-chrome-bug-001-ref.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<link rel="help" href="https://crbug.com/926167">
+<style>
+
+#container {
+  width: 200px;
+  height: 150px;
+  border: 1px solid black;
+  overflow: scroll;
+}
+#target {
+  width: 100px;
+  height: 50px;
+  background: green;
+  transform: scale(4);
+}
+</style>
+<!--  -->
+<div id="container">
+  <div id="target"></div>
+</div>
diff --git a/css/css-scrollbars/scrollbars-chrome-bug-001.html b/css/css-scrollbars/scrollbars-chrome-bug-001.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<title>CSS Overflow: css-overflow-3</title>
+<link rel="author" href="mailto:atotic@google.com">
+<link rel="help" href="https://crbug.com/926167">
+<link rel="match" href="scrollbars-chrome-bug-001-ref.html">
+<meta name="assert" content="scrollbars keep up to date with a changing transform">
+<style>
+
+#container {
+  width: 200px;
+  height: 150px;
+  border: 1px solid black;
+  overflow: scroll;
+}
+#target {
+  width: 100px;
+  height: 50px;
+  background: green;
+  transform: scale(1);
+}
+</style>
+<!--  -->
+<div id="container">
+  <div id="target"></div>
+</div>
+<script>
+  // 1st transform triggers layer creation, and full layout.
+  // 2nd transform just updates overflow, which does not update scrollbars.
+  // This triggers the bug.
+  document.body.offsetTop;
+  document.querySelector("#target").style.transform = "scale(1.5)";
+  document.body.offsetTop;
+  document.querySelector("#target").style.transform = "scale(4.0)";
+</script>