components: Make user_prefs a source_set.

components: Make user_prefs a source_set.

This is a tiny component, it does not need to be a shared libray in the
component build.

BUG=None
R=brettw@chromium.org

Committed: https://crrev.com/f8a72db8313967a512ea94c05b3951c255a4b796
Cr-Commit-Position: refs/heads/master@{#340349}

[brettw, 2015-07-24 19:03:10]

LGTM

[tfarina, 2015-07-24 20:14:13]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2015-07-24 20:14:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1258653002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1258653002/1

[commit-bot: I haz the power, 2015-07-24 22:09:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-24 22:10:00]

Patchset 1 (id:??) landed as
https://crrev.com/f8a72db8313967a512ea94c05b3951c255a4b796
Cr-Commit-Position: refs/heads/master@{#340349}

[dcheng, 2015-07-25 05:21:48]

dcheng@chromium.org changed reviewers:
+ dcheng@chromium.org

[dcheng, 2015-07-25 05:21:48]

This appears to have blown up the tree, e.g.
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%...

For example:
AccountChooserModelTest.RespectsUserChoice (run #1):
[ RUN      ] AccountChooserModelTest.RespectsUserChoice
[585:585:0724/160934:5888688763:FATAL:user_prefs.cc(27)] Check failed:
context->GetUserData(UserDataKey()).
#0 0x7f5cbf9979ee base::debug::StackTrace::StackTrace()
#1 0x7f5cbf9e7cff logging::LogMessage::~LogMessage()
#2 0x7f5cca0583b1 user_prefs::UserPrefs::Get()
#3 0x7f5cca04b105 KeyedServiceBaseFactory::GetAssociatedPrefRegistry()
#4 0x7f5cca04afbe KeyedServiceBaseFactory::RegisterUserPrefsOnContextForTest()
#5 0x7f5cca04c4e0 KeyedServiceFactory::GetServiceForContext()
#6 0x7f5cca40ede7
BrowserContextKeyedServiceFactory::GetServiceForBrowserContext()
#7 0x000004d60166 extensions::ExtensionSystemFactory::GetForBrowserContext()
#8 0x00000525ad50 extensions::ExtensionSystem::Get()
#9 0x00000335c14a TestingProfile::Init()
#10 0x00000335bb34 TestingProfile::TestingProfile()
#11 0x000001a0c78a autofill::(anonymous
namespace)::AccountChooserModelTest::AccountChooserModelTest()
#12 0x000001a0d0ff
autofill::AccountChooserModelTest_RespectsUserChoice_Test::AccountChooserModelTest_RespectsUserChoice_Test()
#13 0x000001a0d0c7 testing::internal::TestFactoryImpl\u003C>::CreateTest()
#14 0x0000015fe5fa
_ZN7testing8internal12InvokeHelperIN16sync_file_system18RemoteServiceStateENSt3tr15tupleIJEEEE12InvokeMethodINS2_25MockRemoteFileSyncServiceEMS9_KFS3_vEEES3_PT_T0_RKS6_
#15 0x0000032f414e
testing::internal::HandleExceptionsInMethodIfSupported\u003C>()
#16 0x0000032e9723 testing::TestInfo::Run()
#17 0x0000032e9cea testing::TestCase::Run()
#18 0x0000032ef07c testing::internal::UnitTestImpl::RunAllTests()
#19 0x000001ab247a
_ZN7testing8internal12InvokeHelperIbNSt3tr15tupleIJEEEE12InvokeMethodI25MockServiceProcessControlMS7_FbvEEEbPT_T0_RKS4_
#20 0x0000032f54ee
testing::internal::HandleExceptionsInMethodIfSupported\u003C>()
#21 0x0000032eed1f testing::UnitTest::Run()
#22 0x0000062ac7a1 RUN_ALL_TESTS()
#23 0x0000062ab8b8 base::TestSuite::Run()
#24 0x0000062b65ed content::UnitTestTestSuite::Run()
#25 0x0000007e1669 base::internal::RunnableAdapter\u003C>::Run()
#26 0x0000007e15cc
_ZN4base8internal12InvokeHelperILb0EvNS0_15RunnableAdapterIMNS_7RunLoopEFvvEEENS0_8TypeListIJPS3_EEEE8MakeItSoES6_S8_
#27 0x0000033c2cd8
_ZN4base8internal7InvokerINS_13IndexSequenceIJLm0EEEENS0_9BindStateINS0_15RunnableAdapterIMN7content17UnitTestTestSuiteEFivEEEFiPS7_ENS0_8TypeListIJNS0_17UnretainedWrapperIS7_EEEEEEENSD_IJNS0_12UnwrapTraitsISF_EEEEENS0_12InvokeHelperILb0EiSA_NSD_IJSB_EEEEEFivEE3RunEPNS0_13BindStateBaseE
#28 0x0000007dfe2e base::Callback\u003C>::Run()
#29 0x0000062a641f base::(anonymous namespace)::LaunchUnitTestsInternal()
#30 0x0000062a62d7 base::LaunchUnitTests()
#31 0x0000033c2aa5 main
#32 0x7f5cb822676d __libc_start_main
#33 0x0000007adba9 \u003Cunknown>

[dcheng, 2015-07-25 05:22:27]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1254123002/ by dcheng@chromium.org.

The reason for reverting is: Try to fix UserPrefs::Get() crashes..