[Runtime] Re-enable seccomp-bpf sandbox on Linux

Chromium for Linux has 2 sandboxes: setuid that creates a chroot like
sandbox and thus requires a setuid helper binary that we don't ship, and the
seccomp-bpf sandbox that was previously disabled for no reason.

I'm enabling the seccomp-bpf sandbox back.
[Extensions] Fix Zombie extension process on Linux after a ctrl+c

On Linux we are currently leaving the extension process alive
even after its parent, the BrowserProcess, was killed with ctrl+c
(^C, or SIGTERM).

We still haven't found a more chromium-ish way of doing this,
so let's stick to prctl.h for now.
[Extensions] Change switch to --disable-extension--process

This will enable the ExtensionProcess (EP) by default for all
platforms, but shouldn't affect Android. On this platform,
XWalkExtensionService::RegisterExtension is called directly,
which makes extensions to be registered on the in_process
XWalkExtensionServer.
[Extensions][Android] Disable ExtensionProcess by default
Merge pull request #585 from wuhengzhi/titleChange

[Android] Add the callback of onTitleChanged in test.
Merge pull request #679 from tmpsantos/sandbox

[Runtime] Re-enable seccomp-bpf sandbox on Linux
[Extensions][Tests] Make ExternalExtension tests use the ExtensionProcess
[Extensions] Use base::GetNativeLibraryName in RegisterExternalExtensionsInDirectory

This will avoid us having problems with .so vs .dll (Linux vs Windows).
[Extensions][Windows] Disable ExtensionProcess for Windows
Merge pull request #676 from jeez/ep-final

[Extensions] Make ExtensionProcess enabled by default
Remove old C API and support code needed for it

Now that we moved old clients to use new C API, we remove the old. See
rationale for our new C API in commit
7300aa3a4f0e5f6754e737a003a4dd67d401bf2f.
Merge pull request #684 from cmarcelo/remove-old-c-api

Remove old C API and support code needed for it
[Android] Enable the geolocation feature.

Some files were copied from the android_webview, like as InMemorySharedPreferences.java, \
XWalkBrowserContext.java, runtime_geolocation_permission_context.cc. They were modified \
according to the current project requirements, remove the jni dependency, since this \
feature is required on other platforms.

BUG=
TEST=build/android/run_instrumentation_tests.py --test-apk XWalkCoreTest \
--verbose -I --num_retries=1 -f testGeolocationPermissionShowPrompt