Suppress Uninitialized error on extensinos_unittsts

BUG=418767
TBR=asargent@chromium.org

Review URL: https://codereview.chromium.org/613843004

Cr-Commit-Position: refs/heads/master@{#297294}

tools/valgrind/drmemory/suppressions_full.txt

@@ -1873,3 +1873,8 @@ pdf.dll!pp::InputEvent_HandleEvent
 ppapi_proxy.dll!ppapi::CallWhileUnlocked<>
 ppapi_proxy.dll!ppapi::proxy::PPP_InputEvent_Proxy::OnMsgHandleFilteredInputEvent
 
+UNINITIALIZED READ
+name=bug_418767
+*!extensions::core_api::cast_channel::CastTransport::SetErrorState
+*!extensions::core_api::cast_channel::CastTransport::Do*Complete
+*!extensions::core_api::cast_channel::CastTransport::On*Result

tools/valgrind/memcheck/suppressions.txt

@@ -3459,3 +3459,10 @@
    fun:_ZN4base19SequencedWorkerPoolC1EmRKSs
    fun:_ZN16sync_file_system13drive_backend14SyncEngineTest5SetUpEv
 }
+{
+   bug_418767
+   Memcheck:Uninitialized
+   fun:_ZN10extensions8core_api12cast_channel13CastTransport13SetErrorStateENS1_12ChannelErrorE
+   fun:_ZN10extensions8core_api12cast_channel13CastTransport1*CompleteEi
+   fun:_ZN10extensions8core_api12cast_channel13CastTransport1*ResultEi
+}