Making VisibleSelection operator== take base and extent into account.

Source/core/editing/VisibleSelection.h

Index: Source/core/editing/VisibleSelection.h
diff --git a/Source/core/editing/VisibleSelection.h b/Source/core/editing/VisibleSelection.h
index 75856ea84e53dc33c3ed5fbc93a903cfc1826c55..f9583eb0217c4e33e4f5af6d57afcad5c9f53ca1 100644
--- a/Source/core/editing/VisibleSelection.h
+++ b/Source/core/editing/VisibleSelection.h
@@ -183,7 +183,7 @@ private:
 inline bool operator==(const VisibleSelection& a, const VisibleSelection& b)
 {
     return a.start() == b.start() && a.end() == b.end() && a.affinity() == b.affinity() && a.isBaseFirst() == b.isBaseFirst()

[yosin_UTC9, 2015/04/16 04:59:04]

if one of selections is null, we don't need to check start/end and base/extent.
So, we could write:

if (a.affinity() != b.affinity() || a.isDirectional() != b.isDirectional())
  return false;

if (a.isNull())
  return b.isNull();

return a.start() == b.start() && a.end() == b.end() && a.base() == b.base() &&
a.extent() == b.extent();

[yosin_UTC9, 2015/04/16 04:59:04]

Since we compare base/extent equality, we don't need to check equality of
|isBaseFirst()|.

[mfomitchev, 2015/04/16 18:11:32]

Added the None check and removed isBaseFirst() check. Other than that, I am not
sure we need to explicitly short-circuit: if any of the == evaluate to false, it
won't evaluate any other == anyway. And it seems that checking start/end
positions first is pretty effective in eliminating unequal results right away.
Even if this makes sense, I don't think it needs to be a part of this CL.

-        && a.isDirectional() == b.isDirectional();
+        && a.isDirectional() == b.isDirectional() && a.base() == b.base() && a.extent() == b.extent();
 }
 
 inline bool operator!=(const VisibleSelection& a, const VisibleSelection& b)