[Mac] Change to detach the web contents view when the panel is not taller than the titlebar.

We used to hide the web contents view in such case but it seems to trigger some bad effect occasionally.

BUG=265932
TEST=existing tests
R=ccameron@chromium.org, dimich@chromium.org

Review URL: https://codereview.chromium.org/22629009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@217139 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/cocoa/panels/panel_window_controller_cocoa.mm

@@ -7,7 +7,6 @@
 #import <Cocoa/Cocoa.h>
 
 #include "base/auto_reset.h"
-#include "base/command_line.h"
 #include "base/logging.h"
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
@@ -31,7 +30,6 @@
 #include "chrome/browser/ui/panels/panel_manager.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/toolbar/encoding_menu_controller.h"
-#include "chrome/common/chrome_version_info.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_view.h"
@@ -809,23 +807,32 @@ NSCursor* LoadWebKitCursor(WebKit::WebCursorInfo::Type type) {
 }
 
 - (void)windowDidResize:(NSNotification*)notification {
-  // This is a temporary check to track down a crash that occurs occasionally
-  // (http://crbug.com/265932).
-  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
-  if (channel == chrome::VersionInfo::CHANNEL_CANARY &&
-      CommandLine::ForCurrentProcess()->HasSwitch("enable-panel-experiment"))
+  // Remove the web contents view from the view hierarchy when the panel is not
+  // taller than the titlebar. Put it back when the panel grows taller than
+  // the titlebar. Note that RenderWidgetHostViewMac works for the case that
+  // the web contents view does not exist in the view hierarchy (i.e. the tab
+  // is not the main one), but it does not work well, like causing occasional
+  // crashes (http://crbug.com/265932), if the web contents view is made hidden.
+  //
+  // The reason for doing this is to ensure that our titlebar view, that is
+  // somewhat taller than the standard titlebar, does not overlap with the web
+  // contents view because the the web contents view assumes that its view will
+  // never overlap with another view in order to paint the web contents view
+  // directly. If we do not do this, some part of the web contents view will
+  // become visible and overlap the bottom area of the titlebar.
+  content::WebContents* webContents = windowShim_->panel()->GetWebContents();
+  if (!webContents)
     return;
-  // Hide the web contents view when the panel is not taller than the titlebar.
-  // This is to ensure that the titlebar view is not overlapped with the web
-  // contents view because the the web contents view assumes that its
-  // view will never be overlapped by another view in order to perform
-  // optimization. If we do not do this, some part of the web contents view
-  // will become visible and overlapp the bottom area of the titlebar.
-  if (WebContents* contents = windowShim_->panel()->GetWebContents()) {
-    BOOL hideContents =
-        NSHeight([self contentRectForFrameRect:[[self window] frame]]) <=
-        panel::kTitlebarHeight;
-    [contents->GetView()->GetNativeView() setHidden:hideContents];
+  NSView* contentView = webContents->GetView()->GetNativeView();
+  if (NSHeight([self contentRectForFrameRect:[[self window] frame]]) <=
+      panel::kTitlebarHeight) {
+    // No need to retain the view before it is removed from its superview
+    // because WebContentsView keeps a reference to this view.
+    if ([contentView superview])
+      [contentView removeFromSuperview];
+  } else {
+    if (![contentView superview])
+      [[[self window] contentView] addSubview:contentView];
   }
 }