Make first-letter style to work with editing

Source/core/rendering/RenderText.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Andrew Wellington (proton@wiretapped.net)
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 510 matching lines @@
     case AlwaysDownstream:
         affinity = DOWNSTREAM;
         break;
     case AlwaysUpstream:
         affinity = VP_UPSTREAM_IF_POSSIBLE;
         break;
     case UpstreamIfPositionIsNotAtStart:
         affinity = offset > box->caretMinOffset() ? VP_UPSTREAM_IF_POSSIBLE : DOWNSTREAM;
         break;
     }
-    return box->renderer()->createPositionWithAffinity(offset, affinity);
+    int textStartOffset = box->renderer()->isText() ? toRenderText(box->renderer())->textStartOffset() : 0;
+    return box->renderer()->createPositionWithAffinity(offset + textStartOffset, affinity);
 }
 
 static PositionWithAffinity createPositionWithAffinityForBoxAfterAdjustingOffsetForBiDi(const InlineTextBox* box, int offset, ShouldAffinityBeDownstream shouldAffinityBeDownstream)
 {
     ASSERT(box);
     ASSERT(box->renderer());
     ASSERT(offset >= 0);
 
     if (offset && static_cast<unsigned>(offset) < box->len())
         return createPositionWithAffinityForBox(box, box->start() + offset, shouldAffinityBeDownstream);
@@ skipping 1311 matching lines @@
 
     SecureTextTimer* secureTextTimer = gSecureTextTimers->get(this);
     if (!secureTextTimer) {
         secureTextTimer = new SecureTextTimer(this);
         gSecureTextTimers->add(this, secureTextTimer);
     }
     secureTextTimer->restartWithNewText(lastTypedCharacterOffset);
 }
 
 } // namespace WebCore