Move to Chromium 38.0.2125.34, the first M38 beta release.

As usual, SIMD support in V8 is disabled while the v8-crosswalk folks
rebase their code.

Relevant, non-extensive list of Chromium CLs which required us to adapt
our code:

  * https://codereview.chromium.org/213583003
  * https://codereview.chromium.org/273223002
  * https://codereview.chromium.org/321423002
  * https://codereview.chromium.org/338373002
  * https://codereview.chromium.org/344493002
  * https://codereview.chromium.org/356713005
  * https://codereview.chromium.org/364123002
  * https://codereview.chromium.org/369703002
  * https://codereview.chromium.org/373623002
  * https://codereview.chromium.org/381113004
  * https://codereview.chromium.org/382143005
  * https://codereview.chromium.org/393653002
  * https://codereview.chromium.org/397243004
  * https://codereview.chromium.org/398243002
  * https://codereview.chromium.org/398503002
  * https://codereview.chromium.org/398873004
  * https://codereview.chromium.org/405633002
  * https://codereview.chromium.org/411283002
  * https://codereview.chromium.org/415423002
  * https://codereview.chromium.org/421613002
  * https://codereview.chromium.org/425653002
  * https://codereview.chromium.org/432553003

Relevant intermediate commit messages from intermediate commits in our
next branch:

[Android] Aligh with new java targets' classes_dir

Chromium has changed java targets' classes_dir to
<intermediate>/classes/2.
It impacts xwalk_native_libraries_java and
xwalk_core_library_java in crosswalk. Changes the
classes_dir of these two targets accordingly.

In addition, use dependent settings of gyp to sync variables
between targets instead of hardcode to avoid similar issues in
future.

--

Gardening M38: Remove classes_dir in gyp files

Upstream removes classes_dir in java.gypi and java_apk.gypi.
Previously, crosswalk relies on it to create xwalk_core_library
and xwalk_runtime_embedded.
For xwalk_core_library, use javac_jar_path instead of classes_dir.
For xwalk_runtime_embedded, the target is not used any more
after xwalk_app_template switch to use xwalk_core_library,
just removed it.

--

Gardening M38: Remove classes_dir in gyp files

Upstream removes classes_dir in java.gypi and java_apk.gypi.
Previously, crosswalk relies on it to create xwalk_core_library
and xwalk_runtime_embedded.
For xwalk_core_library, use javac_jar_path instead of classes_dir.
For xwalk_runtime_embedded, the target is not used any more
after xwalk_app_template switch to use xwalk_core_library,
just removed it.

--

Re-enable WebRTC support on Tizen.

Temporarily roll WebRTC's revision manually from c1696da to cdc3123:
cdc3123 Rename linuxwindowpicker to x11windowpicker & only use it with
        use_x11
ee3ec04 common_audio/signal_processing: Remove macro
        WEBRTC_SPL_UMUL_32_16_RSFT16

cdc3123 is required to fix XWALK-2160 and re-enable WebRTC support, as
libjingle now forces a dependency on the webrtc_base target which was
causing the Tizen build to fail even with -Ddisable_webrtc=1.

See https://code.google.com/p/webrtc/issues/detail?id=3625 and
XWALK-2160.

--

gyp_xwalk: Sync with M38's gyp_chromium.

Sync the script with Chromium commits r279309, r286307, r286632,
r288360, r289094, r289099, r289158, r289546 and r289699.

Most of the changes are related to supporting the --analyzer option and
moving the handling of landmines to a separate file.

--

BUG=XWALK-2160
BUG=XWALK-2431