Web Inspector: Added an option to split Elements and Sources sidebars in two panes.

Web Inspector: Added an option to split Elements and Sources sidebars in two panes.
https://bugs.webkit.org/show_bug.cgi?id=109298.

Patch by Vladislav Kaznacheev <kaznacheev@chromium.org> on 2013-02-15
Reviewed by Vsevolod Vlasov.

Introduced the "Split sidebar" context menu option that splits the horizontal sidebar into two panes.
The width split ratio is 1:1 by default and is preserved when the Inspector window is resized.
Elements sidebar is split into two tabbed panes, Sources sidebar is split into a pane stack and a tabbed pane.

No new tests.

* inspector/front-end/DOMBreakpointsSidebarPane.js:
(WebInspector.DOMBreakpointsSidebarPane.Proxy.prototype._reattachBody):
* inspector/front-end/ElementsPanel.js:
(WebInspector.ElementsPanel.get this):
(WebInspector.ElementsPanel):
(WebInspector.ElementsPanel.prototype._sidebarContextMenuEventFired):
(WebInspector.ElementsPanel.prototype._populateContextMenuForSidebar.toggleSetting):
(WebInspector.ElementsPanel.prototype.get _arrangeSidebarPanes.get this):
(WebInspector.ElementsPanel.prototype.addExtensionSidebarPane):
* inspector/front-end/ExtensionServer.js:
(WebInspector.ExtensionServer.prototype._onCreateSidebarPane):
* inspector/front-end/ScriptsPanel.js:
(WebInspector.ScriptsPanel):
(WebInspector.ScriptsPanel.prototype._appendUISourceCodeItems):
(WebInspector.ScriptsPanel.prototype._contextMenuEventFired):
(WebInspector.ScriptsPanel.prototype._sidebarContextMenuEventFired):
(WebInspector.ScriptsPanel.prototype._populateContextMenuForSidebar.toggleSetting):
(WebInspector.ScriptsPanel.prototype.get _arrangeSidebarPanes.get this):
* inspector/front-end/SidebarPane.js:
(WebInspector.SidebarPane):
(WebInspector.SidebarPane.prototype.expand):
(WebInspector.SidebarPane.prototype.onContentReady):
(WebInspector.SidebarPane.prototype._setExpandCallback):
(WebInspector.SidebarPane.prototype.wasShown):
(WebInspector.SidebarPaneTitle):
(WebInspector.SidebarPaneTitle.prototype._expand):
(WebInspector.SidebarPaneTitle.prototype._collapse):
(WebInspector.SidebarPaneTitle.prototype._toggleExpanded):
(WebInspector.SidebarPaneTitle.prototype._onTitleKeyDown):
(WebInspector.SidebarPaneStack):
(WebInspector.SidebarPaneStack.prototype.addPane):
(WebInspector.SidebarTabbedPane):
(WebInspector.SidebarTabbedPane.prototype.addPane):
* inspector/front-end/SidebarView.js:
* inspector/front-end/SplitView.js:
(WebInspector.SplitView):
(WebInspector.SplitView.prototype.get mainElement):
(WebInspector.SplitView.prototype.get sidebarElement):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@143006 268f45cc-cd09-0410-ab3c-d52691b4dbfc