Use CancellationFlag instead of Lock in PostHelper

XWalkExtensionThreadedRunner have a helper object that runs jobs in
another thread. When threaded runner goes down, we want to
invalidate (cancel) that helper object.

This commit change from using a Lock and changing the runner_ value
inside the helper to simply use CancellationFlag (which boils down to an
atomic operated value).
[Devtools] Show right message when App is inspected already.
To correct a HTML/CSS coding error in Devtools discovery page
[Android] Cancel library-not-found dialog when library installed

For xwalk apps on Android, they will try to find runtime lib at
startup time. If runtime lib not found, an alert dialog will be
prompted for navigating user to download it from play store.

When the app is brought back to the front, it will check
runtime lib's existense. If runtime lib found, the alert dialog
should be automatically canceled.

BUG=https://github.com/crosswalk-project/crosswalk/issues/638
[Extensions] Create the EP<->RP IPC Channel

We create a MODE_SERVER Channel on the ExtensionProcess
and use the BrowserProcess (through ExtensionProcessHost)
to let the RenderProcess know about this ChannelHandle.
[Extension] Create a Client Channel for EP on RenderProcess

For now this MODE_CLIENT channel will use a dummy listener to
receive its messages. It will later be substituted by a
XWalkExtensionClient.
[Extensions] Use the ExtensionsServer from ExtensionProcess to communicate with RP

Now we are using the EP <-> RP IPC Channel to make the ExtensionServer,
from the ExtensionProcess, communicate with its DummyListener running on the
renderer process. We also make it only send the RegisterExtension message
after the RenderProcess has connected to its channel.
[Extensions] Fixing ExtensionProcess channel creation after review

- Adding a function to XWalkExtensionProcessHost that sends the
EP channel handle when ready and it's used by OnRenderProcessHostCreated
and OnRenderChannelCreated;

- Splitting XWalkExtensionProcess::CreateChannel() into 2 more specific
functions: CreateBrowserProcessChannel() and CreateRenderProcessChannel();

- Fixing style issues.
[Android] Add navigation handler for handling platform-specific schemes.

Some platform-specific schemes are needed to be handled, eg, "wtai://", we
provide default navigation handler in XWalkView to support such schemes.

"wtai://" is a protocol scheme that can initiate a dialog with the mobile phone
user whether to place a call to that number, send an SMS message, or store the
number in the address list of the mobile phone.

See: http://www.w3.org/wiki/UriSchemes/wtai

In this patch we support placing a call. And other functions will be added later.

BUG=https://github.com/crosswalk-project/crosswalk/issues/380
[Android] Copy extension related Java files for xwalk core library

This library should include all core Java files. Newly-added Java
files for extension system should also be copied to avoid Java class
missing error.
Merge pull request #671 from yongsheng/master

[Android] Copy extension related Java files for xwalk core library
[Runtime] Add XPK package generate tool

The python script can generate XPK package from Crosswalk application
resources, furthermore, it will generate a RSA private key if it's invalid.
[Tizen] Polish Python code according to Chromium Python style guidelines.

Per Chromium Python style guidelines,
http://www.chromium.org/chromium-os/python-style-guidelines
This CL sets single quote for string values, and sets functions names
with CapWords() style.
Merge pull request #576 from PeterWangIntel/master

[Devtools] Show right message when App is inspected already.
Merge pull request #663 from jeez/eph-channel

[Extensions] Create the EP <-> RP IPC Channel
Merge pull request #587 from cmarcelo/cancellation-flag

Use CancellationFlag instead of Lock in PostHelper
[Extensions] Add an external extensions XWalkExtensionClient to RendererController

XWalkExtensionClient::Initialize(IPC::Sender*) was added so we can:
  1- create a XWalkExtensionClient;
  2- initialize a SyncChannel using the Client as its listener;
  3- initialize the Client by passing the SyncChannel as its Sender.

This change follows exactly how XWalkExtensionServer is designed nowadays.
[Extensions] Don't register external extensions in BP if using EP
[Extensions] Build fix for windows

IPC::ChannelHandle is a struct, not a class.
Merge pull request #674 from jeez/win-fix

[Extensions] Build fix for windows