[DevTools] Extract part of DevTools into inspector app.

Source/devtools/front_end/inspectorStyle.css

Index: Source/devtools/front_end/inspectorStyle.css
diff --git a/Source/devtools/front_end/inspectorStyle.css b/Source/devtools/front_end/inspectorStyle.css
index 7ed9328aef36b9b2cc005cceac79b71b3b5453fd..2e7ca879fb67a14b14726e9da64c22b884ce2d31 100644
--- a/Source/devtools/front_end/inspectorStyle.css
+++ b/Source/devtools/front_end/inspectorStyle.css
@@ -27,6 +27,14 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+.inspector-app-iframe {
+    position: absolute;
+    left: 0;
+    top: 0;
+    width: 100%;
+    height: 100%;
+}
+
 input[type="search"]:focus,
 input[type="text"]:focus {
     outline: auto 5px -webkit-focus-ring-color;