Grab mouse capture in the WM_POINTERDOWN message handler in the omnibox.

chrome/browser/ui/views/omnibox/omnibox_view_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/views/omnibox/omnibox_view_win.h"
 
 #include <algorithm>
 #include <locale>
 #include <string>
 
@@ skipping 1431 matching lines @@
       break;
     default:
       break;
   }
   return DefWindowProc(message, wparam, lparam);
 }
 
 LRESULT OmniboxViewWin::OnPointerDown(UINT message,
                                       WPARAM wparam,
                                       LPARAM lparam) {
-  if (!model()->has_focus())
+  if (!model()->has_focus()) {
     SetFocus();
+    SetCapture();

[sky, 2012/10/11 19:24:25]

Do you need a corresponding ReleaseCapture somewhere now?

[ananta, 2012/10/11 20:04:04]

Added a ReleaseCapture in OnPointerUp.

+  }
 
   if (IS_POINTER_FIRSTBUTTON_WPARAM(wparam)) {
     TrackMousePosition(kLeft, CPoint(GET_X_LPARAM(lparam),
                                      GET_Y_LPARAM(lparam)));
   }
 
   SetMsgHandled(false);
 
   return 0;
 }
@@ skipping 1215 matching lines @@
   return (rect.left - client_rect.left) + (client_rect.right - rect.right);
 }
 
 int OmniboxViewWin::WidthNeededToDisplay(const string16& text) const {
   // Use font_.GetStringWidth() instead of
   // PosFromChar(location_entry_->GetTextLength()) because PosFromChar() is
   // apparently buggy. In both LTR UI and RTL UI with left-to-right layout,
   // PosFromChar(i) might return 0 when i is greater than 1.
   return font_.GetStringWidth(text) + GetHorizontalMargin();
 }