Web Inspector: add button to open Inspector^2

Web Inspector: add button to open Inspector^2
https://bugs.webkit.org/show_bug.cgi?id=175108

Reviewed by Brian Burg.

Source/WebCore:

This patch just exposes a function to the inspector page. No new functionality was added.

* inspector/InspectorFrontendHost.idl:
* inspector/InspectorFrontendHost.h:
* inspector/InspectorFrontendHost.cpp:
(WebCore::InspectorFrontendHost::inspectInspector):

Source/WebInspectorUI:

* UserInterface/Debug/Bootstrap.js:
(updateDebugUI):
(WI.runBootstrapOperations):

* UserInterface/Views/ButtonToolbarItem.js:
(WI.ButtonToolbarItem):
(WI.ButtonToolbarItem.prototype.get label): Deleted.
(WI.ButtonToolbarItem.prototype.set label): Deleted.
* UserInterface/Views/ButtonToolbarItem.css:
(.toolbar .item.button):
(.toolbar .item.button:not(.disabled):active):
(.toolbar .item.button:not(.disabled):matches(:focus, .activate.activated)):
(.toolbar .item.button:not(.disabled):active:matches(:focus, .activate.activated)):
(.toolbar .item.button > .glyph):
(.toolbar .item.button:not(.disabled):active > .glyph): Deleted.
(.toolbar .item.button:not(.disabled):matches(:focus, .activate.activated) > .glyph): Deleted.
(.toolbar .item.button:not(.disabled):active:matches(:focus, .activate.activated) > .glyph): Deleted.
(.toolbar .item.button > .label): Deleted.
* UserInterface/Views/ActivateButtonToolbarItem.js:
(WI.ActivateButtonToolbarItem):
(WI.ActivateButtonToolbarItem.prototype.get label): Deleted.
(WI.ActivateButtonToolbarItem.prototype.set label): Deleted.
* UserInterface/Base/Main.js:
(WI.contentLoaded):
Remove unused `label` parameter from Toolbar objects.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@220235 268f45cc-cd09-0410-ab3c-d52691b4dbfc