Revert of Move JoinString to the base namespace

Revert of Move JoinString to the base namespace (patchset #9 id:160001 of https://codereview.chromium.org/1223153003/)

Reason for revert:
The compilation failure with the following error message:

FAILED: /b/build/goma/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/chrome/common/common.chrome_content_client.o.d -DV8_DEPRECATION_WARNINGS -D_FILE_OFFSET_BITS=64 -DGOOGLE_CHROME_BUILD -DCR_CLANG_REVISION=241602-3 -DENABLE_RLZ -DUI_COMPOSITOR_IMAGE_TRANSPORT -DUSE_AURA=1 -DUSE_ASH=1 -DUSE_PANGO=1 -DUSE_CAIRO=1 -DUSE_DEFAULT_RENDER_THEME=1 -DUSE_LIBJPEG_TURBO=1 -DUSE_X11=1 -DIMAGE_LOADER_EXTENSION=1 -DENABLE_REMOTING=1 -DENABLE_WEBRTC=1 -DENABLE_MEDIA_ROUTER=1 -DUSE_PROPRIETARY_CODECS -DENABLE_PEPPER_CDMS -DENABLE_CONFIGURATION_POLICY -DENABLE_NOTIFICATIONS -DENABLE_HIDPI=1 -DENABLE_TOPCHROME_MD=1 -DUSE_UDEV -DENABLE_TASK_MANAGER=1 -DENABLE_EXTENSIONS=1 -DENABLE_PLUGINS=1 -DENABLE_SESSION_SERVICE=1 -DENABLE_THEMES=1 -DENABLE_AUTOFILL_DIALOG=1 -DENABLE_PROD_WALLET_SERVICE=1 -DENABLE_BACKGROUND=1 -DENABLE_GOOGLE_NOW=1 -DCLD_VERSION=2 -DENABLE_PRINTING=1 -DENABLE_PRINT_PREVIEW=1 -DENABLE_SPELLCHECK=1 -DENABLE_CAPTIVE_PORTAL_DETECTION=1 -DENABLE_APP_LIST=1 -DENABLE_SUPERVISED_USERS=1 -DENABLE_MDNS=1 -DENABLE_SERVICE_DISCOVERY=1 -DENABLE_HANGOUT_SERVICES_EXTENSION=1 -DV8_USE_EXTERNAL_STARTUP_DATA -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DSAFE_BROWSING_SERVICE -DGL_GLEXT_PROTOTYPES -DMOJO_USE_SYSTEM_IMPL -DPROTOBUF_USE_DLLS -DGOOGLE_PROTOBUF_NO_RTTI -DGOOGLE_PROTOBUF_NO_STATIC_INITIALIZER -DSK_SUPPORT_GPU=1 -DSK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS -DSK_LEGACY_SKPOINT3_CTORS -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DU_STATIC_IMPLEMENTATION -DLIBXML_STATIC -DUSE_LIBPCI=1 -DUSE_GLIB=1 -DUSE_NSS_CERTS=1 -DOS_CHROMEOS=1 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DNDEBUG -DNO_UNWIND_TABLES -DOFFICIAL_BUILD -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -D_FORTIFY_SOURCE=2 -Igen -I../.. -I../../skia/config -I../../third_party/khronos -I../../gpu -I../../third_party/WebKit/Source -Igen/protoc_out -I../../third_party/protobuf -I../../third_party/protobuf/src -Igen/chrome -I../../third_party/WebKit -I../../third_party/mojo/src -Igen/third_party/mojo/src -I../../net/third_party/nss/ssl -I../../skia/ext -I../../third_party/skia/include/core -I../../third_party/skia/include/effects -I../../third_party/skia/include/pdf -I../../third_party/skia/include/gpu -I../../third_party/skia/include/lazy -I../../third_party/skia/include/pathops -I../../third_party/skia/include/pipe -I../../third_party/skia/include/ports -I../../third_party/skia/include/utils -I../../third_party/icu/source/i18n -I../../third_party/icu/source/common -I../../third_party/libxml/linux/include -I../../third_party/libxml/src/include -Igen/ui/resources -Igen/extensions -Igen/extensions/strings -I../../third_party/re2 -Igen/policy -Werror -pthread -fno-strict-aliasing -Wall -Wno-unused-parameter -Wno-missing-field-initializers -fvisibility=hidden -pipe -fPIC -Wno-reserved-user-defined-literal -Xclang -load -Xclang /b/build/slave/google-chrome-rel-chromeos/build/src/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang check-templates -fcolor-diagnostics -g -B/b/build/slave/google-chrome-rel-chromeos/build/src/third_party/binutils/Linux_x64/Release/bin -Wheader-hygiene -Wno-char-subscripts -Wno-unneeded-internal-declaration -Wno-covered-switch-default -Wstring-conversion -Wno-c++11-narrowing -Wno-deprecated-register -Wno-inconsistent-missing-override -Wexit-time-destructors -Wno-shift-negative-value -pthread -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/include/nss -I/usr/include/nspr -Wno-header-guard -m64 -march=x86-64 -O2 -fno-ident -fdata-sections -ffunction-sections -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-exceptions -fno-rtti -fno-threadsafe-statics -fvisibility-inlines-hidden -Wsign-compare -std=gnu++11  -c ../../chrome/common/chrome_content_client.cc -o obj/chrome/common/common.chrome_content_client.o
../../chrome/common/chrome_content_client.cc:193:34: error: no matching function for call to 'JoinString'
      std::string codec_string = base::JoinString(
                                 ^~~~~~~~~~~~~~~~

Original issue's description:
> Move JoinString to the base namespace.
>
> Change "Separator" from string to StringPIece (most are constants). Remove char versions for symmetry with SplitString.
>
> Update callers who pass empty separators to use a base::StringPiece()
>
> Change chromecast/base/metrics/cast_metrics_helper.cc to not use JoinString at all and just append to the output (code is simpler and faster).
>
> TBR=zelidrag@chromium.org for chromeos
>
> Committed: https://crrev.com/0eabfa001ba06d3c66992b95b69a988ef0633992
> Cr-Commit-Position: refs/heads/master@{#338762}

TBR=jam@chromium.org,zelidrag@chromium.org,brettw@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/b8788460cebd0e84919246968166c54f900471b2
Cr-Commit-Position: refs/heads/master@{#338770}

[hongchan, 2015-07-14 23:38:15]

Created Revert of Move JoinString to the base namespace

[commit-bot: I haz the power, 2015-07-14 23:38:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1237873004/1

[commit-bot: I haz the power, 2015-07-14 23:41:59]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-14 23:43:06]

Patchset 1 (id:??) landed as
https://crrev.com/b8788460cebd0e84919246968166c54f900471b2
Cr-Commit-Position: refs/heads/master@{#338770}