[Mac] More tweaks to the Lion gesture UI.

chrome/browser/renderer_host/chrome_render_widget_host_view_mac_delegate.mm

 // 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.
 
 #import "chrome/browser/renderer_host/chrome_render_widget_host_view_mac_delegate.h"
 
 #include <cmath>
 
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/debugger/devtools_window.h"
@@ skipping 237 matching lines @@
                               usingHandler:^(CGFloat gestureAmount,
                                              NSEventPhase phase,
                                              BOOL isComplete,
                                              BOOL *stop) {
           if (phase == NSEventPhaseBegan) {
             [historyOverlay showPanelForView:
                 render_widget_host_->view()->GetNativeView()];
             return;
           }
 
+          BOOL ended = phase == NSEventPhaseEnded;
+
+          // Dismiss the panel before navigation for immediate visual feedback.
+          [historyOverlay setProgress:gestureAmount];
+          if (ended)
+            [historyOverlay dismiss];
+
           // |gestureAmount| obeys -[NSEvent isDirectionInvertedFromDevice]
           // automatically.
           Browser* browser = BrowserList::FindBrowserWithWindow(
               historyOverlay.view.window);
-          if (phase == NSEventPhaseEnded && browser) {
+          if (ended && browser) {
             if (goForward)
               browser->GoForward(CURRENT_TAB);
             else
               browser->GoBack(CURRENT_TAB);
           }
 
-          [historyOverlay setProgress:gestureAmount];
-          if (isComplete) {
-            [historyOverlay dismiss];
+          if (isComplete)
             [historyOverlay release];
-          }
         }];
       return YES;
     }
   }
   return gotUnhandledWheelEvent_;
 }
 
 - (BOOL)validateUserInterfaceItem:(id<NSValidatedUserInterfaceItem>)item
                       isValidItem:(BOOL*)valid {
   SEL action = [item action];
@@ skipping 69 matching lines @@
 }
 
 - (void)spellCheckEnabled:(BOOL)enabled checked:(BOOL)checked {
   spellcheck_enabled_ = enabled;
   spellcheck_checked_ = checked;
 }
 
 // END Spellchecking methods
 
 @end