Advance document lifecycle to CompositingClean prior to hit testing

Source/core/dom/DocumentLifecycle.cpp

Index: Source/core/dom/DocumentLifecycle.cpp
diff --git a/Source/core/dom/DocumentLifecycle.cpp b/Source/core/dom/DocumentLifecycle.cpp
index 59346de54fe7f197b9ed219f1e935cf1710852f8..c8c2439730dfd0464af826a49d759700536b6716 100644
--- a/Source/core/dom/DocumentLifecycle.cpp
+++ b/Source/core/dom/DocumentLifecycle.cpp
@@ -130,6 +130,8 @@ bool DocumentLifecycle::canAdvanceTo(State state) const
     if (m_state == CompositingClean) {
         if (state == InStyleRecalc)
             return true;
+        if (state == InPreLayout)

[esprehn, 2015/03/24 23:01:03]

If we're in pre layout tasks why would we advance directly to CompositingClean?
This patch doesn't seem to explain the reason for this.

[qiankun, 2015/03/25 03:13:59]

It allows advancing document life cycle from CompositingClean to preLayout. I
fixed the case calls layout() after hit testing.

There is no bug for hit testing. This change is motivated by
https://codereview.chromium.org/976543002. In order to query compositingState in
collectFragments(), levi@ and chrishtr@ suggested that we should ensure that the
document lifecycle is advanced to CompositingClean prior to hit testing.

+            return true;
         if (state == InCompositingUpdate)
             return true;
         if (state == InPaintInvalidation)