[Android] Implement the http authentication in xwalk default client.

  The implementation is to provide the http anthentication
funtions to support the authentication requirement of some
web site related to username and password, covering the
following:
1 Import and implement a general class of HttpAuthDatabase
  to support common http authentication database interfaces.
  This class imports the android sqlite database to handle
  the username and password data on demand.
2 In default xwalk client, implement the method of
  setHttpAuthUsernamePassword() by calling the related method
  of HttpAuthenDatabase instance to set the username and password.
3 In default xwalk client, implement the method of
  getHttpAuthUsernamePassword() by calling the related method
  of HttpAuthenDatabase instance to query the username and password.

BUG=#784, #787
Fix the issue File Download Crash in Debug mode

Crosswalk hits DCHECK_NE(content::DownloadItem::kInvalidId, id) failed, since
chromium upstream improved the code, we needed to override the virtual function
GetNextId().
Please see: https://codereview.chromium.org/15584002
This CL also fixed FileDownload error in Linux trybots.

https://github.com/crosswalk-project/crosswalk/issues/888
Enable Aura build on all platforms except Android

Enable Aura build on all platforms except Android.
Merge pull request #897 from pozdnyakov/Enable_Aura_except_Android

Enable Aura build on all platforms except Android
Remove GTK code from xwalk

Since we're always using aura on linux desktop, GTK-related code in xwalk is deprecated and should be removed.
[Extensions] Test extensions with nested names

Add a test for nested extension names. This models our use case for
Tizen-Extensions-Crosswalk, that have the "tizen" extension as well as
many "tizen.*" subextensions.

The second test is disabled, but will serve to check whether we load a
"leaf" extension on demand.
Merge pull request #890 from cmarcelo/nested-test

[Extensions] Test extensions with nested names
Merge pull request #896 from yinli/FileDownload

Fix the issue File Download Crash in Debug mode
Bump version to 2.31.18.0
Merge pull request #899 from pozdnyakov/Remove_GTK

Remove GTK code from xwalk
Fix the issue that getUserMedia can't work on Linux, Tizen and Windows platform

This is a general fix on Linux, Tizen and Windows platform, since the chromium rebasing
resulted in this issue.
XWalkMediaCaptureDevicesDispatcher::RunRequestMediaAccessPermission wasn't running.
Merge pull request #901 from yinli/getUserMedia_Linux

Fix the issue that getUserMdeida can't work on Linux, Tizen and Windows ...
[Extensions] Add --enable-loading-extensions-on-demand switch

Runtime switch to protect the implementation of on demand loading of
extensions ("lazy load") until it's done, when we change the semantics
to be --disable.

In the release this feature debuts, we keep the disable switch to allow
QA disable if needed. After we succesfully ship one stable Crosswalk
with the feature (it will be Crosswalk 2), the current plan is to remove
the switch, because we don't intend to keep the codepath for the
non-lazy behavior.
Merge pull request #909 from cmarcelo/load-on-demand-switch

[Extensions] Add --enable-loading-extensions-on-demand switch
[Android] The first step to fix the resource id generation for core library.

Currently the resource ids for org.chromium.ui and org.chromium.content
are not generated so the web app will crash when running. Because
the container can't get the resources and their ids.
This patch is the first step to copy necessary resources from these two
targets to xwalk core library. The next step is to generate the correct
R.java.

BUG=#862
Merge pull request #906 from yongsheng/862

[Android] The first step to fix the resource id generation for core libr...
Bump version to 2.31.19.0
Add application extension and getManifest(), getMainDocument() API support

The application extension is an internal extension to handle application level
APIs(e.g., runtime events, manifest, package management, etc.).

In this commit two APIs is added, one is xwalk.application.getManifest(see
http://developer.chrome.com/apps/runtime.html#method-getManifest), the other is
xwalk.application.getMainDocument(see
http://developer.chrome.com/apps/runtime.html#method-getBackgroundPage).

We use asynchronous calls for both of these two APIs. getManifest() will
retrieve current running application's manifest dictionary value and post the
value to renderer. getMainDocument() utilizes ApplicationNativeModule to get
RenderView from the main document's routing ID, then return its main frame
global JS object.
[Runtime] Add GetApplicationByID in ApplicationService

Using GetApplicationByID replace with the GetApplicationStore, since it's very
dangrous to export the ApplicationStore outside ApplicationService.
[Runtime] Add switch "--list-apps" to list all installed applications from command line

Execute the xwalk with "--list-apps" switch will print all installed applications
information to standared IO stream.