Fix transparent crack at top of page while resizing devtools NSSplitView divider.

chrome/browser/ui/cocoa/dev_tools_controller.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/ui/cocoa/dev_tools_controller.h"
 
 #include <algorithm>
 
 #include <Cocoa/Cocoa.h>
 
@@ skipping 12 matching lines @@
 
 // Minimal height of devtools pane or content pane when devtools are docked
 // to the browser window.
 const int kMinDevToolsHeight = 50;
 const int kMinDevToolsWidth = 150;
 const int kMinContentsSize = 50;
 
 }  // end namespace
 
 
+@interface GraySplitView : NSSplitView
+- (NSColor*)dividerColor;
+@end
+
+
+@implementation GraySplitView
+- (NSColor*)dividerColor {
+  return [NSColor darkGrayColor];
+}
+@end
+
+
 @interface DevToolsController (Private)
 - (void)showDevToolsContents:(WebContents*)devToolsContents
                  withProfile:(Profile*)profile;
 - (void)showDevToolsContainer:(NSView*)container profile:(Profile*)profile;
 - (void)hideDevToolsContainer:(Profile*)profile;
 - (void)resizeDevTools:(CGFloat)size;
 @end
 
 
 @implementation DevToolsController
 
 - (id)init {
   if ((self = [super init])) {
-    splitView_.reset([[NSSplitView alloc] initWithFrame:NSZeroRect]);
+    splitView_.reset([[GraySplitView alloc] initWithFrame:NSZeroRect]);
     [splitView_ setDividerStyle:NSSplitViewDividerStyleThin];
     [splitView_ setVertical:NO];
     [splitView_ setAutoresizingMask:NSViewWidthSizable|NSViewHeightSizable];
+    [splitView_ setDelegate:self];
 
     dockToRight_ = NO;
   }
   return self;
 }
 
+- (void)dealloc {
+  [splitView_ setDelegate:nil];
+  [super dealloc];
+}
+
 - (NSView*)view {
   return splitView_.get();
 }
 
 - (NSSplitView*)splitView {
   return splitView_.get();
 }
 
 - (void)updateDevToolsForWebContents:(WebContents*)contents
                          withProfile:(Profile*)profile {
@@ skipping 137 matching lines @@
     shouldAdjustSizeOfSubview:(NSView *)subview {
   // Return NO for the devTools view to indicate that it should not be resized
   // automatically. It preserves the height set by the user and also keeps
   // view height the same while changing tabs when one of the tabs shows infobar
   // and others are not.
   if ([[splitView_ subviews] indexOfObject:subview] == 1)
     return NO;
   return YES;
 }
 
+-(void)splitViewWillResizeSubviews:(NSNotification *)notification {
+  [[splitView_ window] disableScreenUpdatesUntilFlush];
+}
+
 @end