Web Inspector: Fix keyboard shortcuts for other platforms
https://bugs.webkit.org/show_bug.cgi?id=120657

Reviewed by Timothy Hatcher.

Handling keyboard shortcuts according to the current platform.

* UserInterface/InspectorFrontendHostStub.js:
(.WebInspector.InspectorFrontendHostStub.prototype.loadResourceSynchronously):
(.WebInspector.InspectorFrontendHostStub.prototype.platform): Added. Return the
current platform.
* UserInterface/KeyboardShortcut.js:
(WebInspector.KeyboardShortcut.Modifier.CommandOrControl): Added. Created keyboard
modifier to return Control or Command key according to current platform.
* UserInterface/ContentBrowser.js:
(WebInspector.ContentBrowser): Returning Control or Command key for keyboard
shortcuts according to current platform.
* UserInterface/DebuggerSidebarPanel.js:
(WebInspector.DebuggerSidebarPanel): Ditto.
* UserInterface/FindBanner.js:
(WebInspector.FindBanner): Ditto.
* UserInterface/JavaScriptLogViewController.js:
(WebInspector.JavaScriptLogViewController): Ditto.
* UserInterface/LogContentView.js:
(WebInspector.LogContentView): Ditto.
* UserInterface/Main.js:
(WebInspector.contentLoaded): Ditto.
* UserInterface/ResourceSidebarPanel.js:
(WebInspector.ResourceSidebarPanel): Ditto.