[LyX/master] Revert "Now math previews are correctly updated when replacing math contents inside"

[Scott Kostyshak]

commit 62190855bfee2a3c08abff5f62a9b1226aab7f63
Author: Scott Kostyshak <skost...@lyx.org>
Date:   Fri Nov 13 00:54:15 2015 -0500

    Revert "Now math previews are correctly updated when replacing math 
contents inside"
    
    Updating all previews (even if only one has changed) is more costly
    than I thought. Thanks to Guillaume for tracking down this
    performance issue.
    
    This reversion is related to the reversions at 358745d0 and
    a7a14395. See also #7242 and #9855.
    
    This reverts commit 29948eec26ffc90bdfe0b853aa79d30cfa36c08d.

diff --git a/src/lyxfind.cpp b/src/lyxfind.cpp
index f46bed9..d7038de 100644
--- a/src/lyxfind.cpp
+++ b/src/lyxfind.cpp
@@ -1425,7 +1425,6 @@ static void findAdvReplace(BufferView * bv, 
FindAndReplaceOptions const & opt, M
        LYXERR(Debug::FIND, "After pos adj cur=" << cur << " with depth: " << 
cur.depth() << " and len: " << sel_len);
        bv->putSelectionAt(DocIterator(cur), sel_len, !opt.forward);
        bv->processUpdateFlags(Update::Force);
-       bv->buffer().updatePreviews();
 }