Add test for paint underinvalidation fix with animated transform overflow.

third_party/WebKit/Source/web/tests/sim/SimCompositor.cpp

Index: third_party/WebKit/Source/web/tests/sim/SimCompositor.cpp
diff --git a/third_party/WebKit/Source/web/tests/sim/SimCompositor.cpp b/third_party/WebKit/Source/web/tests/sim/SimCompositor.cpp
index 23a105cd9670e131486ec65b5917a79e8cf10f9a..43ac8d1e0ce2edc275161a822cf490f7a212fe98 100644
--- a/third_party/WebKit/Source/web/tests/sim/SimCompositor.cpp
+++ b/third_party/WebKit/Source/web/tests/sim/SimCompositor.cpp
@@ -79,14 +79,13 @@ void SimCompositor::clearSelection() {
   m_hasSelection = false;
 }
 
-SimDisplayItemList SimCompositor::beginFrame() {
+SimDisplayItemList SimCompositor::beginFrame(double dt) {
   DCHECK(m_webViewImpl);
   DCHECK(!m_deferCommits);
   DCHECK(m_needsBeginFrame);
   m_needsBeginFrame = false;
 
-  // Always advance the time as if the compositor was running at 60fps.
-  m_lastFrameTimeMonotonic = monotonicallyIncreasingTime() + 0.016;
+  m_lastFrameTimeMonotonic = monotonicallyIncreasingTime() + dt;
 
   m_webViewImpl->beginFrame(m_lastFrameTimeMonotonic);
   m_webViewImpl->updateAllLifecyclePhases();