[Extensions][Windows] Enable ExtensionProcess for Windows
Clean up in use of DesktopRootWindowHostXWalk

DesktopRootWindowHostXWalk serves as our "desktop environment"
per scree, which is somewhat similar to the X11 window manager
concept.

The specialized version of DesktopRootWindowHost (*XWalk) in
our situation, is created as part of DesktopNativeWidgetAura
initialization, but requires build system changes for doing so.

This patch cleans up part of the code, making it very clear
why we manually creates DesktopRootWindowHostXWalk and why it
works. It also removes the ::Create method which is called
by DesktopRootWindowHost because it is wrongly named, and if
named correctly it will conflict with the symbol from *X11.
[Tizen] Integrate crosswalk with Tizen input method system.

Crosswalk needs to be integrated with Tizen input system,
so that users could e.g., enter text into input field element.

This CL integrates chromium input method system with Tizen IME
using SCIM / ISF (Input Service Framework) interfaces. SCIM is
running as a daemon and communicates with clients over socket.
Whenever client is asking to show input panel (VKB), input panel
is shown and key presses are sent back to the client over socket.
This CL implements basic functionality that will be extended in
following input method patches. Crosswalk opens virtual keyboard
and user can type-in latin characters. Unicode characters,
pre-editing and other advanced features are not implemented.

InputMethodScim - Realization of chromium InputMethod interface.
ScimBridge - Class that communicates with Tizen ISF and forwards key
events to chromium input method / text clients.
Merge pull request #681 from alexshalamov/integrate_tizen_ime

[Tizen] Integrate crosswalk with Tizen input method system.
Merge pull request #701 from kenchris/cleanupaura

Clean up in use of DesktopRootWindowHostXWalk
[Tizen] Add pkgconfig(scim) to the list of crosswalk dependencies.
Merge pull request #710 from alexshalamov/add_scim_dependency

[Tizen] Add pkgconfig(scim) to the list of crosswalk dependencies.
Update the documentation about Sync Messages

Now it is made clear that replies to Sync Messages can be sent after
the handler of the call has returned.

This is valid because we can only have one Sync Message going on at
any time (the renderer is blocking).
Merge pull request #712 from vcgomes/execution-model-docs

Update the documentation about Sync Messages
Clean the house in XWalkExtension(Instance)

- Updated the comments to be more on par with existing implementation;
- Added an overview at the top;
- Removed unused includes, forward declarations;
- Moved Callback types to XWalkExtensionInstance;
- Shuffled some functions to their appropriate places.

This patch shouldn't change code behavior.
Rename XWalkExternalContext to XWalkExternalInstance

The concept is now called Instance instead of Context. This allow us to
remove the typedef hack in XWalkExternalAdapter.
Rename xwalk_external_context.cc/h to xwalk_external_instance.cc/h

To match the class names. Patches are separated so the name change in
code is easier to review. This patch just renames the files and updates
references to it.
[Tizen] Use InputMethodSCIM instead of InputMethodScim in factory.
Merge pull request #714 from alexshalamov/fix_class_name_in_inputfactory

[Tizen] Use InputMethodSCIM instead of InputMethodScim in factory.
Merge pull request #686 from jeez/enable-ep-win

[Extensions][Windows] Enable ExtensionProcess for Windows
Merge pull request #711 from cmarcelo/extension-cleanups

Extension cleanups
Avoid creating cursors on Tizen

The X11 on Tizen doesn't support showing cursors and crashes when
trying to create cursors of a different scale than 1.0.

This allows --force-device-scale-factor= to work.
Merge pull request #715 from kenchris/cursors

Avoid creating cursors on Tizen
Change DesktopRootWindowHostTizenX11 from DesktopRootWindowHostXwalk.

After this CL, only Tizen(tizenos=1) uses DesktopRootWindowHostTizenX11. Desktop
linux uses DesktopRootWindowHostX11.
We have changed DesktopRootWindowHostTizenX11 only for Tizen.
1. multi touch support
2. remove cursor logic
We will change DesktopRootWindowHostTizenX11 only for Tizen.
1. device scale factor support
2. application resume and pause support
3. etc..
So only Tizen should use this class.