Allow enabling WebSockets from Labs Preferences

Change-Id: Ia0dc06cbd4f2e8e340a8f8ee910a6310a5079d79
Browser hang when playing video in popup window

The function "onShowCustomView" in WebChromeClient of subwebview is
not implemented, and makes the fullscreen layout can't be set. Here
we call main webview's onShowCustomView.

Change-Id: I576e017be61bca0775b5cc897f35092a63c6dca7
Author: weiweix.ji <weiweix.ji@intel.com>
Signed-off-by: Xiaokang Qin <xiaokang.qin@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 51736
Browser freezes when adding new incognito tab after removing it

When do layout, the position of new tab may be changed since other tab
closed, we need to get the position again at the time.

Change-Id: Ia5bcc15a0074678f401d6b3e93026e5ef5d2af7d
Author: weiweix.ji <weiweix.ji@intel.com>
Signed-off-by: Xiaokang Qin <xiaokang.qin@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 66643
Handle DownloadManager expceptions

Handles illegal state exceptions thrown by DownloadManager
on two ocassions:
* the directory sdcard/Downloads is an ordinary file
* could not create dirctory sdcard/Downloads

Change will log an error, additionally toast with information
will pop up.

Change-Id: If853d3218a188bc77c187362a70697126b90989d