[Android] Allow use non Activity context to create ContentVideoView

ContentVideoView is making an assertion that the context used to create
it is an Activiy, which xwalk doesn't meet. So xwalk crashes when
trying to fullscreen a video.

Why upstream makes the assertion:
ContentVideoView will use context to getSystemService(WINDOW_SERVICE),
which requires an Activity context.

Why xwalk can work as well as break the assertion:
In xwalk case, it's using a MixContext which although the base context
is not an Activity, but the getSystemService call will be bridged to
an Activity finally.

Why can't this be upstreamed:
The real assertion is getSystemService must be called on an Activity,
upstream uses the equivalence that the context should be an Activity
is reasonable for most cases.

For more detail discussion, please refer upstream CL at:
https://codereview.chromium.org/67763004/

Since there's no easy way to detect whether the WindowManager got from
the Context is good or not, this patch to remove the assertion have
to stay in our fork.

BUG=https://crosswalk-project.org/jira/browse/XWALK-171
[Linux] Enabling Hardware Acceleration with Libva in linux-x86.

This commit is not upstreamable.

Currently, VAAPI only enabled for ChromeOS and Windows on
upstream. Although the ChromeOS uses same libva API as
common linux world, upstream refuesed to enable it for linux
common with maintainence concern. Refer to
"https://codereview.chromium.org/16430003/" for more details.

Upstream confirm VAVDA will continue to be restricted to
CrOS/X86 for dev & testing only and not for chromium road map.
So we maintain it for Crosswalk and that will benifit
linux with VAAPI installed and includes Tizen.
[Android] Backport Chromium r237215

This is to fix crash when multi touch on Android devices
previous to 4.2.2.

Origin commit log:
    [Android] Record MotionEvent times for pre-4.2.2 ScaleGestureDetector bug.

    Android's pre-4.2.2 ScaleGestureDetector failed to properly record MotionEvent
    times.  This leads to problems, as the detector's event time is used to assign
    the synthesized gesture event time.  Record the MotionEvent time prior to
    feeding it to the ScaleGestureDetector.

    BUG=323108

    Review URL: https://codereview.chromium.org/85453004
    git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237215 0039d316-1c4b-4281-b951-d872f2087c98

BUG=https://crosswalk-project.org/jira/browse/XWALK-458
Merge pull request #88 from wang16/touch_crash

[Android] Backport Chromium r237215
Merge pull request #87 from wang16/full_screen_video

[Android] Allow use non Activity context to create ContentVideoView
[SysApps] Expose ffmpeg function signatures needed by Device Capabilities API

We need these functions in to get the list of Codecs available in the
system for getAVCodecs(). If we ever fork ffmpeg, we can just remove
this patch and add the signatures directly at the ffmpeg's signature
list.
Merge pull request #90 from tmpsantos/ffmpeg_sigs

[SysApps] Expose ffmpeg function signatures needed by Device Capabilities API
[Tizen][Performance] Enable Accelerated 2D Canvas.

If GPU context can be lost, Accelerated 2D Canvas is disabled, because there is
no way to recover Accelerated 2D Canvas when GPU crashes. Currently, only EGL
backend marks GPUInfo::can_lose_context true (means Accelerated 2D Canvas cannot
be enabled). However, interestingly, Android and ChromeOS mark it false to take
advantage of Accelerated 2D Canvas without fallback solution. They just take a
risk.

So Tizen also takes a risk like Android and ChromeOS. It is worth to do it
because performance improvement is very significant (2~3 times).

Measurement data:
1. http://www.craftymind.com/factory/guimark3/vector/GM3_JS_Vector.html
Software Canvas : 14.91 FPS
Accelerated 2D Canvas : 44.82 FPS
2. http://www.craftymind.com/factory/guimark3/bitmap/GM3_JS_Bitmap.html
Software Canvas : 17.16 FPS
Accelerated 2D Canvas : 54.58 FPS
3. http://www.craftymind.com/factory/guimark3/compute/GM3_JS_Compute.html
Software Canvas : 19.36 FPS
Accelerated 2D Canvas : 39.18 FPS

BUG=https://crosswalk-project.org/jira/browse/XWALK-531,
https://crosswalk-project.org/jira/browse/XWALK-73
Merge pull request #91 from ds-hwang/a2dc

[Tizen][Performance] Enable Accelerated 2D Canvas.
Merge pull request #85 from zhang-qing/master2.1

[Linux] Enabling Hardware Acceleration with Libva in linux-x86.
Revert "x11: Fix a few touch-event related issues:"

This reverts Chromium commit f8a9520395d7a1e478e6f134d1bb016f45087d00.

[Tizen][Temp] Re-enable pinch zoom in Tizen 2.X.

Chromium had hack to emulate multi touch using XIButton events. However,
unfortunately, above commit dropped the hack, because Chromium officially
supports XInput 2.2 or above.

Tizen 2.X has used the hack because Tizen 2.X does not support XInput2.2 touch
event.
In detail,
1) Tizen 2.1 supports XInput2.1.
2) Tizen 2.2.1 supports XInput2.2, but uses XI_Button event instead of XI_Touch
event.

Temp:
So this PR reverts the commit to support multi touch to Tizen 2.X. If we bump
up to Tizen 3.0, this commit can be removed.

BUG=https://crosswalk-project.org/jira/browse/XWALK-445