[Tizen] Fix Glib assertion due to appcore_context.

This patch get rid of following log:
[ERROR:browser_main_loop.cc(228)] GLib: g_source_destroy: assertion `source != NULL' failed

AppcoreContext::Initialize() fails when we launch xwalk in the shell. e.g. > xwalk
It is because appcore_init() can success only if registered application (e.g.
web applications) is launched.

This patch handles the exception that AppcoreContext::Initialize() fails.
Merge pull request #931 from hmin/refine-test-target

[Android] Refine the xwalk_core_test_apk target
[Android] Remove the wrong dependence in runtime client test apk.

This patch will resolve the issue about wrong dependence in the runtime
client test apk.
In file CrossPackageWrapper.java, the constructor function "CrossPackageWrapper()"
has the judgement about the class loaded. In shared mode, the core shell is not
needed for the runtime client test shell.

BUG=#916
Merge pull request #917 from wuhengzhi/shared_issue

[Android] Remove the wrong dependence in runtime client test apk.
[Android] Fix #705 to support multiple frames for extension mechanism

When there are multiple frames in one page, extension instance will
be created for each frame. But as internal WebFrame is not exposed
in Java side, there is no way for Java side to identify which
instance to send message. This patch exposed instanceID up to Java
side when it receives message which can be used to identify the
target instance when post message to JavaScript side. What's more
a new interface "broadcastMessage" was added to meet the requirement
that Java side may need to broadcast message to all exiting instances.

Changed interfaces for Java extension:
1. postMessage(String msg) -> postMessage(int instanceID, String msg)
2. onMessage(String msg)   -> onMessage(int instanceID, String msg)
3. onSyncMessage(String msg) -> onSyncMessage(int instanceID, String msg)
4. new added: broadcastMessage(String msg)

BUG=#705
[Android] Fix text selection menu being auto-dismissed in some cases

In previous xwalk implementation, the load operation will trigger
a pair of clear/request focus operation. Which makes the text selection
context menu hide immediately after it shows sometimes.

The fix is to only request focus when loading url.
Merge pull request #950 from wang16/cordova_txt_sel

[Android] Fix text selection menu being auto-dismissed in some cases
Merge pull request #935 from ds-hwang/appcorebug

[Tizen] Fix Glib assertion due to appcore_context.
Merge pull request #907 from DonnaWuDongxia/multi-frame-support-in-one

[Android] Fix #705 to support multiple frames for extension mechanism
[Android] Implement setNetworkAvailable method in XWalkView

The setNetworkAvailable method allows XWalkView embedder to trigger
window.online/offline event and set navigator.onLine property on JS side when
the network connection is up or down. This fix is to implement this method by
adding a render process observer on native side to watch the network availability
change notification from browser process. At present, it is only used by Android
port.

BUG=https://github.com/crosswalk-project/crosswalk/issues/880
TEST=org.xwalk.core.xwview.test.SetNetworkAvailableTest