Enable fullscreen support

Always allow the tab to go fullscreen. Explicit call to
exit fullscreen is added.  Fullscreen layout logic moved
to base ui class.

Change-Id: I4474d90f99bf4753dedbe453b21f126668c40f64
diff --git a/src/com/android/browser/UI.java b/src/com/android/browser/UI.java
index a374203..5aefd0b 100644
--- a/src/com/android/browser/UI.java
+++ b/src/com/android/browser/UI.java
@@ -137,6 +137,7 @@
     boolean dispatchKey(int code, KeyEvent event);
 
     void setFullscreen(boolean enabled);
+    void showFullscreen(boolean show);
 
     void translateTitleBar(float topControlsOffsetYPix);