Revert of [Sync] Add size and crc32c to AttachmentId.

Revert of [Sync] Add size and crc32c to AttachmentId. (patchset #8 id:140001 of https://codereview.chromium.org/982883002/)

Reason for revert:
Broke build on iOS_Device

http://build.chromium.org/p/chromium.mac/builders/iOS_Device/builds/26684/steps/compile/logs/stdio

Undefined symbols for architecture armv7:
  "syncer::Attachment::CreateFromParts(syncer::AttachmentId const&, scoped_refptr<base::RefCountedMemory> const&, unsigned int)", referenced from:
      syncer::(anonymous namespace)::MockAttachmentStore::RespondToRead(std::__1::set<syncer::AttachmentId, std::__1::less<syncer::AttachmentId>, std::__1::allocator<syncer::AttachmentId> > const&) in attachment_service_impl_unittest.o
      syncer::(anonymous namespace)::MockAttachmentDownloader::RespondToDownload(syncer::AttachmentId const&, syncer::AttachmentDownloader::DownloadResult const&) in attachment_service_impl_unittest.o
      syncer::gtest_case_AttachmentStoreTest_::Write_NoOverwriteNoError<syncer::InMemoryAttachmentStoreFactory>::TestBody() in in_memory_attachment_store_unittest.o
      syncer::OnDiskAttachmentStoreSpecificTest_MismatchedCrc_Test::TestBody() in on_disk_attachment_store_unittest.o
      syncer::gtest_case_AttachmentStoreTest_::Write_NoOverwriteNoError<syncer::OnDiskAttachmentStoreFactory>::TestBody() in on_disk_attachment_store_unittest.o
  "syncer::CreateAttachmentIdProto()", referenced from:
      syncer::AddAttachment(sync_pb::AttachmentMetadata*, bool) in directory_commit_contribution_unittest.o
      syncer::DirectoryUpdateHandlerProcessUpdateTest_ProcessAndApplyUpdatesWithAttachments_Test::TestBody() in directory_update_handler_unittest.o
      syncer::DirectoryUpdateHandlerApplyUpdateTest_SimpleConflictDifferentAttachmentMetadata_Test::TestBody() in directory_update_handler_unittest.o
      syncer::DirectoryUpdateHandlerApplyUpdateTest_SimpleConflictSameAttachmentMetadataDifferentOrder_Test::TestBody() in directory_update_handler_unittest.o
      syncer::AttachmentIdProtoTest_UniqueIdFormat_Test::TestBody() in attachment_id_proto_unittest.o
      syncer::AttachmentIdProtoTest_CreateAttachmentMetadata_NonEmpty_Test::TestBody() in attachment_id_proto_unittest.o
      syncer::SyncManagerChangeProcessingTest_AttachmentMetadataOnlyChanges_Test::TestBody() in sync_manager_impl_unittest.o
      ...
  "syncer::AttachmentId::Create()", referenced from:
      syncer::(anonymous namespace)::SyncDataTest_CreateLocalDataWithAttachments_Test::TestBody() in sync_data_unittest.o
      syncer::AttachmentDownloaderImplTest_HappyCase_Test::TestBody() in attachment_downloader_impl_unittest.o
      syncer::AttachmentDownloaderImplTest_SameIdMultipleDownloads_Test::TestBody() in attachment_downloader_impl_unittest.o
      syncer::AttachmentDownloaderImplTest_RequestAccessTokenFails_Test::TestBody() in attachment_downloader_impl_unittest.o
      syncer::AttachmentDownloaderImplTest_URLFetcher_BadToken_Test::TestBody() in attachment_downloader_impl_unittest.o
      syncer::AttachmentDownloaderImplTest_URLFetcher_ServiceUnavailable_Test::TestBody() in attachment_downloader_impl_unittest.o
      syncer::AttachmentDownloaderImplTest_NoHash_Test::TestBody() in attachment_downloader_impl_unittest.o
      ...
ld: symbol(s) not found for architecture armv7
clang:error: linker command failed with exit code 1 (use -v to see invocation)

Original issue's description:
> [Sync] Add size and crc32c to AttachmentId.
>
> The purpose of this change is to ensure that if a client knows about an
> attachment (i.e. has an AttachmentId or AttachmentIdProto) it will know
> the attachment's size even if the attachment has never been available on
> the local device.
>
> The idea is that by storing size locally, we can simplify remote storage
> management.
>
> Move crc32c out of Attachment now that it's part of AttachmentId.
>
> BUG=464431
>
> Committed: https://crrev.com/23ae3128db0d84a6b1ffa640568a5ec90cfc8808
> Cr-Commit-Position: refs/heads/master@{#319794}

TBR=pavely@chromium.org,maniscalco@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=464431
Committed: https://crrev.com/eb83b6cff47a33585e4d315f1517eaff14132bb5
Cr-Commit-Position: refs/heads/master@{#319807}

[dgrogan, 2015-03-10 01:32:17]

Created Revert of [Sync] Add size and crc32c to AttachmentId.

[commit-bot: I haz the power, 2015-03-10 01:32:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/995683002/1

[commit-bot: I haz the power, 2015-03-10 01:34:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-10 01:35:29]

Patchset 1 (id:??) landed as
https://crrev.com/eb83b6cff47a33585e4d315f1517eaff14132bb5
Cr-Commit-Position: refs/heads/master@{#319807}