[MemSheriff] Suppress uninit reads in SpeechRecognitionAudioSinkTest

TBR=burnik@chromium.org
BUG=422164

Review URL: https://codereview.chromium.org/645793002

Cr-Commit-Position: refs/heads/master@{#299045}

tools/valgrind/drmemory/suppressions_full.txt

@@ -1860,3 +1860,8 @@ pdf.dll!pp::InputEvent_HandleEvent
 ppapi_proxy.dll!ppapi::CallWhileUnlocked<>
 ppapi_proxy.dll!ppapi::proxy::PPP_InputEvent_Proxy::OnMsgHandleFilteredInputEvent
 
+UNINITIALIZED READ
+name=bug_422164
+...
+content.dll!content::WebRtcLocalAudioTrack::Capture
+*!content::SpeechRecognitionAudioSinkTest*

tools/valgrind/memcheck/suppressions.txt

@@ -3485,3 +3485,10 @@
    fun:_ZNSt4listI13scoped_refptrIN5media10VideoFrameEESaIS3_EE9push_backERKS3_
    fun:_ZN5media14VideoFramePool8PoolImpl13FrameReleasedERK13scoped_refptrINS_10VideoFrameEE
 }
+{
+   bug_422164
+   Memcheck:Uninitialized
+   ...
+   fun:_ZN7content21WebRtcLocalAudioTrack7CaptureEPKsN4base9TimeDeltaEibb
+   fun:_ZN7content30SpeechRecognitionAudioSinkTest*
+}