Implement a Hit Test Cache.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index d85fa40c092391c457b3c51c2864d547ea6f4d7e..cafc5a4edb63f3772d2c02291cabc248a1f4d840 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -1227,7 +1227,7 @@ PassRefPtrWillBeRawPtr<Range> Document::caretRangeFromPoint(int x, int y)
     if (!layoutView())
         return nullptr;
 
-    HitTestResult result = hitTestInDocument(this, x, y);
+    HitTestResult result = hitTestInDocument(this, x, y, true);

[Rick Byers, 2015/06/05 20:48:59]

This pattern is generally frowned upon in Google C++, see the true/false part of
http://google.github.io/styleguide/cppguide.html#Implementation_Comments

If skipping the cache is unusual, then I'd suggest having a
hitTestInDocumentNoCache method and leaving the 3 arg method alone.  Alternately
you could use an enum instead of a bool or (usually lowest preference) add a
comment at each call site saying what the true/false means.

[esprehn, 2015/06/06 21:14:29]

Yes, please no bools like this.

[dtapuska, 2015/06/09 18:21:23]

Done.

[dtapuska, 2015/06/09 18:21:23]

Done.

     PositionWithAffinity positionWithAffinity = result.position();
     if (positionWithAffinity.position().isNull())
         return nullptr;