Revert of Sync starting language and input method preferences (patchset #14 id:360001 of https://codereview.chromium.org/312023002/)

Reason for revert:
Causes NULL pointer dereference.

#0  chromeos::input_method::(anonymous namespace)::CheckAndResolveLocales (languages=0x0)
    at ../../chrome/browser/chromeos/input_method/input_method_syncer.cc:58
#1  0x00007f9466f9ddd2 in Run (this=<optimized out>) at ../../base/callback.h:396
#2  base::(anonymous namespace)::PostTaskAndReplyRelay::Run (this=0x647e3eb28c0)
    at ../../base/threading/post_task_and_reply_impl.cc:42
#3  0x00007f9466fa1257 in Run (this=0x7f9454cb1b10) at ../../base/callback.h:396
#4  base::SequencedWorkerPool::Inner::ThreadLoop (this=0x647e2117000, this_worker=this_worker@entry=0x647e34f5190)
    at ../../base/threading/sequenced_worker_pool.cc:760
#5  0x00007f9466fa199d in base::SequencedWorkerPool::Worker::Run (this=0x647e34f5190)
    at ../../base/threading/sequenced_worker_pool.cc:507
#6  0x00007f9466fa1d51 in base::SimpleThread::ThreadMain (this=0x647e34f5190) at ../../base/threading/simple_thread.cc:60
#7  0x00007f9466f9db30 in base::(anonymous namespace)::ThreadFunc (params=<optimized out>)
    at ../../base/threading/platform_thread_posix.cc:80
#8  0x00007f94654ae321 in start_thread (arg=0x7f9454cb2700) at pthread_create.c:309
#9  0x00007f94649527ed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Original issue's description:
> Sync starting language and input method preferences
>
> Users who use additional Chromebooks or who recreate their accounts have
> to manually set up their preferred languages, input methods and IMEs on
> each device, because only the locale (display language) syncs.
>
> We don't forcibly keep these settings in sync because different machines
> may use different built-in or peripheral keyboards. But we can make the
> set-up process smoother if we know what settings the user chose most
> recently.
>
> This CL creates syncable of the language and input
> methods preferences, so the server always has the latest changes.
>
> When, and only when, a user logs in and syncs for the first time on a
> device, we take the local variants the user has already chosen for this
> machine, and we add to them the global variants that come down from
> sync. This only happens at most once. It should only be additive, not
> remove any chosen settings.
>
> Some caveats:
>  * If the user makes a change to one language/input setting, sync all
>    three interdependent settings so the sync server's settings are
>    always internally consistent.
>
> BUG=298345
> R=nkostylev@chromium.org, yukishiino@chromium.org, hajimehoshi@chromium.org
> CC=nona@chromium.org
>
> Committed: https://crrev.com/cceac6fae685fd86d6f347d6712886549e372231
> Cr-Commit-Position: refs/heads/master@{#306164}

TBR=hajimehoshi@chromium.org,alemate@chromium.org,shuchen@chromium.org,yukishiino@chromium.org,dzhioev@chromium.org,dpolukhin@chromium.org,michaelpg@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=298345

Review URL: https://codereview.chromium.org/756363003

Cr-Commit-Position: refs/heads/master@{#306233}

1 files changed, 0 insertions, 4 deletions

diff --git a/chrome/common/pref_names.h b/chrome/common/pref_names.h
index 26e8364..b71bcfa 100644
--- a/chrome/common/pref_names.h
+++ b/chrome/common/pref_names.h
@@ -194,12 +194,8 @@ extern const char kLanguagePreviousInputMethod[];
 extern const char kLanguageHotkeyNextEngineInMenu[];
 extern const char kLanguageHotkeyPreviousEngine[];
 extern const char kLanguagePreferredLanguages[];
-extern const char kLanguagePreferredLanguagesSyncable[];
 extern const char kLanguagePreloadEngines[];
-extern const char kLanguagePreloadEnginesSyncable[];
 extern const char kLanguageEnabledExtensionImes[];
-extern const char kLanguageEnabledExtensionImesSyncable[];
-extern const char kLanguageShouldMergeInputMethods[];
 extern const char kLanguageRemapCapsLockKeyTo[];
 extern const char kLanguageRemapSearchKeyTo[];
 extern const char kLanguageRemapControlKeyTo[];