Alternative: access the WebContentsView directly without an interface method.

chrome/browser/ui/cocoa/extensions/shell_window_cocoa.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.
 
 #include "chrome/browser/ui/cocoa/extensions/shell_window_cocoa.h"
 
 #include "base/mac/mac_util.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/cocoa/browser_window_utils.h"
@@ skipping 54 matching lines @@
   const CGFloat kWindowBorderRadius = 3.0;
   [[NSBezierPath bezierPathWithRoundedRect:[view bounds]
                                    xRadius:kWindowBorderRadius
                                    yRadius:kWindowBorderRadius] addClip];
   [[NSColor whiteColor] set];
   NSRectFill(rect);
 }
 
 @end
 
+@interface ControlRegionView : NSView
+@end
+@implementation ControlRegionView
+- (BOOL)mouseDownCanMoveWindow {
+  return NO;
+}
+- (NSView*)hitTest:(NSPoint)aPoint {
+  return nil;
+}
+@end
+
+@interface NSView (WebContentsView)
+- (void)setMouseDownCanMoveWindow:(BOOL)can_move;
+@end
+
 ShellWindowCocoa::ShellWindowCocoa(Profile* profile,
                                    const extensions::Extension* extension,
                                    const GURL& url,
                                    const ShellWindow::CreateParams& params)
     : ShellWindow(profile, extension, url),
       attention_request_id_(0) {
   // Flip coordinates based on the primary screen.
   NSRect main_screen_rect = [[[NSScreen screens] objectAtIndex:0] frame];
   NSRect cocoa_bounds = NSMakeRect(params.bounds.x(),
       NSHeight(main_screen_rect) - params.bounds.y() - params.bounds.height(),
@@ skipping 16 matching lines @@
     CGFloat max_width = max_size.width() ? max_size.width() : CGFLOAT_MAX;
     CGFloat max_height = max_size.height() ? max_size.height() : CGFLOAT_MAX;
     [window setContentMaxSize:NSMakeSize(max_width, max_height)];
   }
 
   if (base::mac::IsOSSnowLeopardOrEarlier() &&
       [window respondsToSelector:@selector(setBottomCornerRounded:)])
     [window setBottomCornerRounded:NO];
 
   NSView* view = web_contents()->GetView()->GetNativeView();
-  [view setFrame:[[window contentView] bounds]];
   [view setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
-  [[window contentView] addSubview:view];
+  if (params.frame == ShellWindow::CreateParams::FRAME_CHROME) {
+    [view setFrame:[[window contentView] bounds]];
+    [[window contentView] addSubview:view];
+  } else {
+    NSView* web_contents_view =
+        web_contents()->GetView()->GetNativeView();
+    DCHECK([web_contents_view
+        respondsToSelector:@selector(setMouseDownCanMoveWindow:)]);
+    [web_contents_view setMouseDownCanMoveWindow:YES];
+    NSView* frameView = [[window contentView] superview];
+    [view setFrame:[frameView bounds]];
+    [frameView addSubview:view];
+    [[window standardWindowButton:NSWindowZoomButton] setHidden:YES];
+    [[window standardWindowButton:NSWindowMiniaturizeButton] setHidden:YES];
+    [[window standardWindowButton:NSWindowCloseButton] setHidden:YES];
+
+    // TODO(jeremya): this is a temporary hack to allow moving the window while
+    // we still don't have proper draggable region support.
+    NSView* controlRegion = [[ControlRegionView alloc] init];
+    [controlRegion setFrame:NSMakeRect(0, 0, NSWidth([frameView bounds]),
+                                       NSHeight([frameView bounds]) - 20)];
+    [controlRegion setAutoresizingMask:
+        NSViewWidthSizable | NSViewHeightSizable];
+    [frameView addSubview:controlRegion];
+    [controlRegion release];
+  }
 
   window_controller_.reset(
       [[ShellWindowController alloc] initWithWindow:window.release()]);
   [[window_controller_ window] setDelegate:window_controller_];
   [window_controller_ setShellWindow:this];
 }
 
 bool ShellWindowCocoa::IsActive() const {
   return [window() isKeyWindow];
 }
@@ skipping 190 matching lines @@
   return [window_controller_ window];
 }
 
 // static
 ShellWindow* ShellWindow::CreateImpl(Profile* profile,
                                      const extensions::Extension* extension,
                                      const GURL& url,
                                      const ShellWindow::CreateParams& params) {
   return new ShellWindowCocoa(profile, extension, url, params);
 }